Syncing failed: Traceback ... Unknown response code: 400

This seems to be an error that occurred just recently (but seems to persist already a while longer for others).

Here is the log from the error:

Syncing failed:
Traceback (most recent call last):
  File "aqt\", line 376, in _sync
  File "aqt\", line 356, in _abortingSync
  File "anki\", line 120, in sync
  File "anki\", line 614, in sanityCheck2
  File "anki\", line 624, in _run
  File "anki\", line 559, in req
  File "anki\", line 498, in assertOk
Exception: Unknown response code: 400

There has been one suggested fix in some other threads:

  1. run these commands in the debug console :
mw.col.db.execute("delete from revlog where type > 4")

This only works temporarily until you add new cards…

  1. fix database , full sync

This also only works temporarily (it might be the same as 1 , I’m not sure what the commands in (1) do exactly…)

  1. Suggested was to update Anki to the newest version, however this is something that I can not do because I’m using legacy addons (“older” addons that don’t work with the newest version) , also the cards I made with these addons do not render or render with bugs in the newest version. So using the newest version is out of question for me.

What system am I running anki on and what verison am I using?

Has anybody found a working and lasting workaround for this issue?