What is the exact sequence of events?
This error message seems to suggest a thread is panicking when you are syncing, it doesn’t have any context to do with adding a note/card.
Do you get this message when you are saving a note or can you create new notes on desktop Anki, but then you get this message when you try to sync?
Also for future reference please put error messages in backticks like this when posting to the forum. It makes them display nicer:
```
error message
```