I had this problem on a recent project. Though I can’t say I solved the problem, I did learn a few things that might help.
1st we did have a very heavy audio edit. So the advice above may well help.
2nd, the problem didn’t seem to be linked to the computer. We could move to a different computer (same drives though) and still have the issue.
3rd, I thought the issue might have something to do with the display of video during things like rolling and moving clips around the timeline, especially when it affected adjacent clips. The one workaround I did come up with was to use some alternative trimming techniques:
Instead of dragging sections around the timeline, use copy and paste, and instead of rolling out to extend a shot, use the extend feature. These two things seemed to work without delay.
If you do solve the problem please let me know!
Will