Hi Andrew_ACHZ, the issue you're describing should be resolved by resetting the vault, and then re-synchronizing to restore your passwords. To do this, please open Passwords through Internet Security. Please leave Passwords locked (or lock it if you have it unlocked), and click "Settings" in the top right > click the "Reset Avast Passwords and delete my data" link. You can then set the Master Password again, and re-sync the PC. There is a very slight chance that this may not resolve the issue correctly on the first attempt; if it does not, I'm afraid that you might need to follow the process multiple times to force Passwords to reset correctly.
The cause of the issue has been fixed, and it should not reoccur again once it's been resolved now.