Can't access photos album when uploading to apps (Instagram, Twitter etc)

This has been sending me insane for months.

I have an iPhone 11 pro, with all the latest updates, but quite a large amount of photos + videos in my iCloud, which is nearing the 2TB limit.

For around 6+ months, I have not been able to upload any photos or videos to an app from any other album, other than from my Recents. This includes favourites, older folders, shared folders etc. Whenever I try, I get the spinning wheel of death forever - I have left it sit there for hours and nothing. I simply cannot even access albums from the upload screen at all!

This is especially frustrating as I usually save the photos and videos I want to post to social media in their own album so they are edited and sorted and now I cannot even do this anymore as I can't access these albums when it comes to posting.

I have installed, uninstalled, cleared the cache, et all. And it makes no difference. I am worried it has to do with the size of my iCloud but I am not sure.

Does anyone have any ideas? I have searched for solutions to this for so long!