The engine thread sends a lot of updates to the main thread. This works well as long as no other thread sends also changes to the main thread.
If a low prio thread is sending updates, and is inhibited by an other thread, than the engine thread is locked, waiting for the higher and low prio thread.
Loading a Track sends a lot of changes to the GUI.
This can be explained by the CO looking.
The engine thread sends a lot of updates to the main thread. This works well as long as no other thread sends also changes to the main thread.
If a low prio thread is sending updates, and is inhibited by an other thread, than the engine thread is locked, waiting for the higher and low prio thread.
Loading a Track sends a lot of changes to the GUI.