So even though I should be working on my Shri Krishna thread, I'm working on a new thread which is if Uttar Ramayan is an interpolation or not. Unlike other threads, I will present arguments for both sides here. Let's begin.

So first, the contradictions from Valmiki Ramayan itself i.e. the previous Kands contradicting Uttar Ramayan.

1 & 2. Phal Shruti/फलश्रुति (the end of a work) happened in Yuddha Kanda. In no other work you will find this in the middle of a work.

1 & 2. Yuddha Kanda mentions that Prabhu's reign lasted for tend thousand years and everybody lived for thousands of years (which contradicts the Shambuka story)

1. When Ravana asks Hanuman ji to be killed, Vibhisana informs no messengers have been killed in this manner and Ravana changes his mind.
2,3&4. Yet, Ravana kills an envoy of Kubera in presence of Vibhishan in Uttar Kand which is far earlier than Sundar Kand's time.

1. In Aranya Kand, Ravana is introduced as invincible to all (Devtas, Rakshas etc)
2,3. Yet, Ravana is unable to beat Yama who actually makes him flee from fight and Brahma had to intervene to stop him from killing Ravana.

1. Ravana is unable to do Bali's task
2,3,4. Ravana is defeated by KapilDev (Don't laugh)

1,2,3. Devtas overpowered Ravana until Indrajit saves him by capturing Indra.

1. Ravana defeated by Kartavirya Arjuna

2,3,4. Defeated by women of Shwet Deep like an insect

Those are a lot of defeats for an invincible warrior like Ravana.

1. In Kishkindha Kanda, Hanuman is unhurt by Vajra of Indra and only Brahma/Indra gave him boons.

2,3,4. Hanuman ji was actually killed and Brahma actually resurrected him and all devtas gave him boons

Continued

Now, from Mahabharat. BORI edition which is the most researched and reputed to be authentic version of Mahabharat.

Ramayan is narrated three times in Mahabharat. All stop at the pattabhishekam of Prabhu.

1st Instance, Rama went to heaven after killing Ravana

Informed again by Hanuman Ji to Bhima (here it is mentioned that Prabhu reigned for 11 thousand years though)

Again, no mention of Uttar Kand

Next is detailed description of Ramayan by Sage Markandeya. Again, no details of Uttar Kand.

Now, from a different perspective. 5 years ago the oldest manuscript of Ramayan was found (believed to be from 6th Century AD) and guess what, it does not has either Bal Kand or Uttar Kand in it. https://timesofindia.indiatimes.com/city/kolkata/6th-century-Ramayana-found-in-Kolkata-stuns-scholars/articleshow/50227724.cms

From https://valmikiramayan.net/ , the below excerpt shows why they have not included Uttar Kand in their database.

Now some counters to this proposistion.

Brahmarshi Shatavadhani Shanmukha Sharma declared that Uttar Kand is authentic. https://www.youtube.com/watch?time_continue=2&v=_QmoJGtVG2c&feature=emb_logo

Karpatri ji maharaj also confirmed the same.

There's also mention of Shambuk Vadh in Bhagvatam and later purans as well but this is all I could find on Uttar Kand.

IMO, it has too many discrepancies to be an authentic Valmiki creation. All of you can make up your own mind.

@PranjalUvaach @Sai_swaroopa @AndColorPockeT