Hi and welcome,
Most often, this happens, if you have a Mackie Control Device as a Remote Control enabled and your MIDI Port is set as an Input (by accident).
Open Studio > Studio Setup. Can you see Mackie Control in the Remote Devices folder here? If yes, double check, the MIDI Input is set to None, or just remove the Mackie Control device completely.
If this is not the case, double check all MIDI Remote devices here in the folder.
Last option would be to check the Preferences > MIDI > MIDI Filter. Make sure MIDI Controllers filter is not enabled or specifically CC64 is not filtered out here.