My audio balance is reset whenever I startup audacity. I usually have it set to 100 left, 90 right to compensate for unbalanced headphones. I am using version 2.3.2 on the most recent version of Windows 10.
Audacity does not specifically reset the audio balance, it just creates a new connection to the sound card. Some sound card drivers reset themselves when this happens. I think this is an intended feature in the sound card driver. The sound card drivers are not part of Audacity, they are part of the operating system.
The best “fix” for this would be to get yourself a pair of headphones that work properly (are balanced).