Bug: Syncing failed, traceback

[abdo]

This may be relevant:

KeyError when syncing older clients

@abdnassar20160885 updating to the latest Anki should make the error go away. You can then rename the problem deck and downgrade again if you wish (note the warning on https://changes.ankiweb.net/#/) @andrewsanchez This is probably caused by a parent deck with different capitalisation, which newer Anki versions accept but older ones do not. It would be good if this could be fixed in the deck you’re distributing so others don’t have the same issue

Also see When problems occur - Frequently Asked Questions