Test it in a new User Space
NB 210312: version 0.1. Images and additional details, grace and flavour still to be added to this post...
Start this test in Menu > System Preferences > Users and Groups. Unlock the padlock with your admin password, then click the + in the bottom left under the user list to create a new user. Create a standard user with no iCloud sign in, and note what password you set for it. Quit all your apps. Copy the track or project you want to work with onto a USB stick or external drive, then disconnect all your external devices, including non-apple mice, keyboards, etc. Finally, Menu > Restart.
If your Mac automatically logs you back in to your workspace after the restart, Menu > Log Out of your account again.
From the select user screen, click into the new user account, and after a pause you’ll be presented with a setup wizard. Please go with the standard settings, but anything optional, like iCloud, or Siri, elect to skip this page without setting anything up. Eventually you’ll be at a new empty desktop. Open your Applications folder or use Spotlight to launch any applications you need for testing.
Our aim here is to discover whether the problem we're working on solving occurs in a clean new space, so please eliminate as much as possible all 3rd party tools and plugins while we do this test.
Now check to see if the problem you were having occurs in this new workspace. Make notes and screen snapshots.
When you've finished testing, copy your notes and snapshots onto a USB stick, Menu > Log Out, and log in to your normal workspace.