Sounds like something is playing with your faders. Settings can be changed during an update.
In Logic, call main menu "Logic Pro > Control Surfaces > Rebuild Defaults".
Then go to main menu "Logic Pro > Control Surfaces > Setup" and if there is a device, delete it.
Check if the problem is gone.
If not, I suggest to install
Snoize Midi Monitor and switch on "MIDI Sources" and "Spy on output to destinations". This displays everything that enters and leaves the Mac and MIDI traffic between all application ports. If the disturbance is NOT internal in Logic, you should see it in MIDI Monitor.
If the problem still persists and MIDI Monitor is totally quiet while Logic runs, the issue is likely in Logic or in your Logic project. Check again if there is automation. To be sure that it isn’t hidden, you may call main menu "Mix > Delete Automation > Delete all Track Automation". Look at MIDI regions for region automation. You can disable regions (default ctrl-M) or delete them if you don’t need them to test the playback. If you have MIDI FX plugins in Instrument tracks, disable them to prevent sending data to faders.