Timing goes wonky when soloing a high hat track

This is a bit of a weird bug, and it isnt too much of a buzzkill, but it definitely is an annoyance. I’ve experienced it before when generating sounds with 3rd party vst instruments, but i am now getting it in a project using only the included steinberg plug-ins. I’ve included a video to demonstrate the issue, because its a bit difficult to describe.

The problem happened when I already had a full project started, but even after I trimmed out the send/insert-fx (and all the other audio tracks) it persisted (got worse actually). Here is the video I made to demonstrate:
http://youtu.be/bRzDx0twpGI

The video shows the one high hat track being all sketchy. Then I pop in a percussion track, which is working fine, then the high hat gets added back and you can hear it all sounds wrong. Strangely enough, when i hit undo a few time to bring back the rest of the project, the timing gets normal again…

Before I go through the detailed list of how I got to this point, has anyone else encountered a similar problem? I might just be a bit of an idiot with settings.

Open history and see where it goes wrong.