I work with the paint tool, the same way always. Recently I experience that when using "background"label the software resets it to label 295 - the one I used previously with treshold tool.
The reset occurs while actually the left button of the mouse is being pushed. Reseting the label manually usually helps but not always - sometimes I need to reset the tool itself. Restart, OS restart does not help. Reinstall was not tried yet.
Additional Information
I have been using the same method on many datasets for weeks, nothing changed, but the bug suddenly appeared today.
Can you see if the 'smudge' option is checked? When this mode is active, the paint color is set to the value at the location where you click (allowing you to easily add/remove).
Let me know if it's not the smudge and we can look deeper.
