A serious problem reported

I have met this trouble several times =(
Some of my cards disappeared after being created, then the software showed a message like this:

Anki 2.1.54 (b6a7760c) Python 3.9.7 Qt 6.3.1 PyQt 6.3.1
Platform: Windows 10
Flags: frz=True ao=False sv=2
Add-ons, last update check: 2022-11-22 19:43:06

Unknown error

Please help me to fix this. Thanks!

Are you sure the cards actually disappeared? Did you try finding them in the Browse screen?

That error is probably unrelated. It was reported multiple times recently and I’ve hit several times randomly.

I think I’ve finally gotten to the bottom of that error - it appears to be a Chromium thing. As @abdo says, it’s unlikely to have any effect on your cards.