i have the same Problem
at home i use Cloudron 4.4.4 there int runs fine, but yesterday i installed a new clorudron installation v. 4.4.5 and ther i have problems with collabora.
when i open a word file from nextcloud the first time it opens, but when i close the file and 30s later i open it again collabora doesnt load, it stays at 1% loading and i cant opan any other file.
I've tried disabling all the other addons in Nextcloud, but no dice. I looked in the logs and there's nothing out of the ordinary.
Girish, I tried to replicate it on your setup, but I can't find anywhere to enable Collabora. I have the option where the documentation you posted says it should be on my Nextcloud instance, but on yours it's not there.