Moving clips in Montage

Today Wavelab decides it doesn’t like me moving clips horizontally in the montage. I’m mastering an album and every time I try to move a clip, even slightly, it allows me to move it so far then the spinning wheel activates and I have to wait 15 seconds or so. Then I can move it a little more, its very annoying. Same when fading at the start or end of a clip. Each clip has third party plugs such as Ozone 8, Fab Filter PQ3, DMG Equilibrium, Softube. But previously all have worked fine. Restart does not fix the problem. Are there any preferences worth clearing?

Are there other operation that cause this? Like resizing a clip? Like adding a marker?
How many clips do you have, approximately?

There were 11 clips. It was happening when I moved clips, resized clips, or faded in/out clips.

Small montage then. I must say I have no clue.
If you quit WaveLab, restart, and edit the montage without ever starting playback, do you get the same problem?