Instagram posting issue

For almost 1 year i have this issue with my account.
Once or twice a month im not able to upload videos on my account.
Sometimes its for 24 hours sometimes for 3 days or longer.
When i'm unable to post videos i still can upload pictures and i also can upload stories.
When im able to post again all my engagement has dropped and must build up everything.
It's so annoying.
I've reported this problem on Instagram maybe 200 times, but they did nothing about it.
I cleared the cache, updated the app, I even bought a new phone, i did everything to fix it.
Nothing was fixing this problem.

Does anybody know what's wrong with my account and what to do about it?

Have you tried uploading via any web app? I suggest you should try windowed app from your PC if it lets you upload.