Rogue CC messages - how to troubleshoot?

Really rough week in DAW world for me. Multiple “MIDI gremlins” seem to have infected my system. Win 10, Cubase 12.03. I’m getting unwanted CC messages transmitted on transport stop, track selection, and at other as yet undetermined times. Using the Midi Monitor as an insert, I can see the messages. For example: CC20 is being set to 127 when I click on a Garritan VST instrument track. Why? I’m also getting some other seemingly random controllers transmitted when I record (cc57/58 I think? - not at my DAW) I have numerous midi devices including a Kurzweil K2600 controller, Metagrid Pro, Behringer X-touch, RME interface, etc.
The Midi Monitor app does not show which PORT a message is coming from, so I can’t figure out where these gremlins are originating. Any suggestions much appreciated!

One option would be to disconnect your MIDI controllers one after another and see if the problems stop. Then you know if it is one of the devices.
Or you could set the input of your MIDI/instrument tracks not to “all devices”, but to none or a selected device and see if that makes a difference.