Changing plugin parameters in GUI sends MIDI CC data

Hi folks, I’ve found something weird in 15.0.21 on my Mac. When moving knobs inside of a plugin (FabFilter, UAD, etc.), Cubase seems to be sending MIDI CC info to the track it’s on. For example, if I have a sustained strings patch that I’m trying to EQ with a UAD 1081 EQ plugin (or FabFilter Pro-Q 4), I’ll hold down a sustained chord and press the sustain pedal, then go to work on sweeping frequencies to get the sound I want. As soon as I touch a knob in the plugin window (using the mouse), it sounds like the dynamics (which are on CC1) drop down to very low, and need to be brought back up with a CC fader. Looking in the MIDI Monitor plugin, I can see that CC 1 is being sent a value of 0, then a value of 9, CC21 is sent a value of 10, and CC11 is sent 16. This is something that is new to me, although I’m on a new computer and Cubase install. No MIDI inserts are enabled to change things up, and I have a bunch of MIDI Remotes in place (which are having all sorts of issues but I don’t know if they’re affecting this). Anyone have any ideas? I can work around it, but it’s super annoying.

This sounds like you have set the midi input port for your tracks to “All MIDI Inputs” and at the same time you have loopback MIDI Ports in your MIDI Remotes.
In this case, when you have bound a MIDI CC message from a MIDI Remote to something, say a parameter of a vst FX plugin, and if you have set the MIDI Remote to output back, this CC message will get passed to the track as well.
That’s my shot in the dark, perhaps some screenshots would be useful, especially if what I described is not the case.