I was able to sync just fine on 2.1.30, maybe the problem is that I updated to 2.1.35? Because the changes to my collection were so little.
It is very unlikely that I exceeded some media-size limit, because my media folder’s size went up from ~6.45GB to 6.48GB in the time when I could sync… to now that I can’t sync.
Edit 2:
I just downgraded to Anki 2.1.30 and the problem persists… I suppose it’s related to some recent change to the syncing server?
Edit 3:
I used the button to delete unused media, suddenly my media folder’s size went from 6.5GB to 1.4GB… but the ‘too large’ message persists.
edit 4:
one thing that maybe I should mention, is that I’m clicking the ‘upload to ankiweb’ button:
It is not possible to adjust AnkiWeb’s limit, but you can export some of the content, and delete it after importing it into a separate profile. After creating a separate AnkiWeb profile and uploading the content there, if you wish to update your existing shared decks, please provide a list to me and I’ll transfer them over to your other account.