Volume keys and menubar volume slider out of sync with one another?

I'm seeing a weird issue where if I adjust the volume first using the menubar volume slider, then the volume keys (or vice-versa): the volume will reset to 100%, then start being adjusted from there. If I use only one or the other to change the volume there's no problem — it's only if I toggle between the two ways of changing the volume that the reset happens.

I'm using RehabMan's VoodooPS2Controller instead of Acidanthera's VoodooPS2. With Acidanthera's the mouse freezes if I try to use any gesture. (For the record, the issue happens with both of them.)

For sound I'm using AppleALC.

Has anyone else had this problem? I had it on Mojave as well, now same thing on Catalina.