ok I'm... I have no words.
whoever worked on wiring in this apt before me (but long after those who built it) used a screw terminal in a junction box.
and into that screw terminal they put what? some wires twisted together, quite badly.
and in the other side? bingo. aluminium!

the cables that go into that junction box is kept on the wall by screws that are placed close enough to the ceiling that the cable is trapped between the screw head and the wall. fourteen of them, instead of like three runs of cable channel.

on the left, three mystery wires in decaying cloth insulation go into the wall. on the right, it's phase, neutral and protective earth.
there has been no protective earth spec'd when the house was built. none of the mystery wires cannot possibly be protective earth. what

since people required photographic proof, here it is, mystery junction box

when the lights are on, all three wires are at the same potential -and- my indicator screwdriver says they're all live. when the lights are off there's 220Vac between BLU and BRN, and 10Vac (what) between BLU and G/Y.
I don't even know.

when I poked with a meter, it made an omnious crackling sound and the lights started to flicker so I'm gonna go out on a limb and say this requires replacing right about fucking now

there's a fan in the wall near the light switch. if I turn the fan on, precisely one ceiling lamp also turns on. the same ceiling lamp turns on if I flip the switch as well.
here I filmed it

I think at this point I need less an "electrician" and more an "exorcist". I'll call the local church

update

oh look the ceiling lamp wiring is also... like that

I did some measuring and -of course- the light switch is inserted in the zero circuit. so the lamp is energized when it's turned off. this isn't even the Carter system they just wired it backwards

in order to rewire this circuit I flipped off one of the switches in the distribution box. kitchen and bathroom lighting and -all- sockets went dead but living room and bedroom lighting stayed on. what

why are all sockets and precisely two out of four ceiling lamps are on a single 16A breaker. why is the bathroom socket (and absolutely nothing else) that has only a low-power washing machine on its own 16A circuit. why is none of this shit behind a GFCI

this wire (that's at *best* 1.5sqmm) goes into electricity meter and then supplies three 16A circuits. both the wire feeding it and the one going out of the meter are far thicker.
is it supposed to blow like a fuse before any of the three breakers trip? I won't be surprised

of -course- since the power into the apartment goes directly through a pair of twisted Al wires--there's no breaker before the meter, though the code requires one--I have no way of fixing this short of getting out dielectric gloves and working on this shit live.
Do Not Want

"oh look a piece of tape i bet that's just junk let me rem..."
so the person who installed the lamp managed to cut the insulation of wire that DID NOT HAVE OUTER PVC SHEATH.
HOW. HOW ARE YOU THIS BAD AT IT

if this house wasn't slated for demolition in several years (no one in the government can coherently say when, only that it is. they used to say this year but then they did cosmetic repair instead, because that makes sense) I would literally just replace all wiring and appliances

honestly tempted to do it anyway but that's like 30-50m of new wiring to put in cable channels and it's both expensive (copper aint cheap) and labor intensive so I'll reuse the old wiring in walls on the assumption that LED lamps are just not enough current, and redo junctions

correction: that breaker switched off all sockets except precisely two completely arbitrary ones https://twitter.com/whitequark/status/1013856560970457088

so basically there's both lighting and sockets in apparently random arrangement on two 16A circuits and there's a third one that powers nothing but a washing machine and bathroom mirror light. because that makes sense.

hellooo there, flying spaghetti monster inside the ceiling lamp. i don't even want to think what hides in the other lamps

I -very- gently pulled at one of the wires going into the screw terminal and it literally just fell out. THIS IS FINE

replaced it all with fresh, not horribly oxidized copper wiring (the one that was screwed in was pretty much black) that's crimp terminated on both ends and then goes into a Wago spring clamp
not the prettiest job but it won't catch fire for sure

the mechanical skills of the person who installed the lamp are on par with electrical. the mounting holes don't lie on the line drawn under the lamp. they aren't parallel to the walls (or anything else anywhere) either

the old insulation (unidentifiable crumbling polymer under unidentifiable crumbling cloth braiding) was in an extremely bad state so I gave it a makeover with some (correctly colored) heatshrink

Wago CAGE-CLAMP 222 series is spec'd for aluminium, see Wago website https://www.wago.com/global/installation-terminal-blocks-and-connectors/compact-splicing-connector/p/222-413 https://twitter.com/11rcombs/status/1013886151336382465

mystery of the hot G/Y conductor: solved
I will find the trash who has worked on wiring in this house, and I will skewer him on a hot protective earth wire

to recap: the brown wire here is -neutral-, and blue and green-yellow are switched, and normally hot because they're energized through the lamp.
the G/Y wire in the junction box misses a chunk of insulation in the middle, too, just for kicks

I don't think I can tear up walls here so I did the next best thing: switched G/Y to be neutral and indicated the real purpose of wiring with a heatshrink sleeve

when they say "you can twist copper" they don't mean twist LIKE THIS

in case you thought this thread can't get any worse, we have a code violation bingo!
behold: exactly 5cm of copper wire extremely badly twisted together with decaying aluminium wire. there was enough length to not do this extension, he could have just put the junction box higher

also the decaying aluminium wire was load-bearing: the junction box was "fixed" to the wall with a single screw (naturally, not going through the hole specifically meant for a screw) but mostly held in place by wiring

by the way, directly above the load-bearing junction box with the aluminium-copper twist there was a polystyrene foam ceiling tile, glued to it badly enough that it fell off and is now solely supported by wiring that rests on threads of screws mounted into the wall

I mean, saying that the aluminium-copper twist was "in" the junction box is doing it a favor. it was "near" the junction box. "in the general area" is perhaps a good way to describe it.

more photos of the mystery junction box. looks like there's another generation of wiring going somewhere... down. I do not know if it is hot, and I dare not check. I do not know where it goes either

as you can see, this junction box has three exposed wires. left to right.
1: neutral.
2: living room ceiling light 1.
3: living room ceiling light 2.
4: bedroom ceiling light and -all bedroom sockets-.
yes. the ENTIRE BEDROOM, including SOCKETS is designed for SWITCHED NEUTRAL.

*wakes up*
i'm this close to giving up. not because i can't fix this--even more depressingly, the fix is near trivial far as i can see--but because of a severe, life-threatening shortage of even.
specifically...

based on the appearance of the junction, either the original builders set up this switched neutral thing, or someone else after them has deliberately (you can't do this accidentally) swapped phase and neutral in the main distribution box
and i don't know which option is worse

i will never make fun of anything related to computers again because no thing in the entire history of computing was done as badly and as hazardously as wiring in this house
yes, i know about therac 25. this is more like a fractal therac 25.

I opened the only circuit in the apartmet with apparently intact grounding and not only the copper wiring is improperly terminated (it ah... fell out when I opened the socket), but also the protective earth is broken in at least two independent points

no, ${anonymous_electrician_who_i_know_for_sure_has_a_state_license}, you do not crimp wire ferrules with -pliers-. not now, not ever.

well this would certainly explain why a correctly wired socket in the kitchen had phase on the proper contact in spite of the cable going to the distribution box being connected backwards (phase and neutral swapped)
same licensed electrician btw

please note the single screw that pretends to keep it in place and, yet again, load-bearing wiring

to be clear, yes, the multistrand copper cable from the distribution box goes through the bathroom socket, is poorly squished into a socket that is designed for singlestrand copper exclusively, and, after going through socket contacts, swaps phase and neutral and continues on

well, and -this- would certainly explain why there's an earth fault. the ... creature who did this part of wiring removed the insulation with a knife on all of phase, zero and ground, phase shorted to ground and burned it off.
no GFCI, nothing to prevent this

I thought the sixty year old aluminium wires twisted together with copper wires that melted into a blob stuffed in a screw terminal would be the worst I see here but the ten year old completely new wiring somehow manages to be even worse

I could literally replace all wiring in this apartment with one huge extension cord christmas tree and it would be less hazardous. by a large margin.

have some more load-bearing aluminium wiring in a screw terminal

the styrofoam is for improved flammability