Since the update to 12.1.0 there has been a bug related to audio track effects (I've specifically found it using the multiband compressor), but haven't tried to reproduce with other effects.
Basically, when re-opening premiere again after working on a project with a multiband compressor effect on a track, the effect won't be doing anything. In order to get it to work, I'll have to go into the mixer and toggle the preset to something else like "raise vocals" and then toggle it back to what it originally was (for me, "Broadcast"). Obviously, this is really inconvenient, as I have to do it every time I re-open a project. Though, an even much bigger issue is if other editors are opening the project, unaware of the issue, and changing the mix. I'll come in later and the mix will be totally off because it's not taking into account the compressors that were supposed to be on the track.