Another bug, seemingly one introduced with Everett because I don't recall seeing anything like this for a while before.
 

 
Simply put - I select 2 clips, slip-edit the start, and when I release the mouse, the bottom one has gained an unwanted snap offset, and the top one has moved the audio by the amount of that snap offset. It's probably significant that these 2 clips are linked, and I suspect that Sonar is failing to notice that I just want exactly the same operation applied to both clips, and is doing something weird by slip-editing one, adding a relevant snap offset to the other, then slip-editing that other one (and thereby getting it wrong). Evidence of the 'adding a snap offset' theory (I edit one clip, deselect it, then show that a snap offset has appeared on the other):
 

 

I create linked audio clips fairly often and regularly see the 'unwanted' snap offset when I slip-edit either of them, so it's not a new thing. And I personally think it's just a visual representation of how much the original clip was slip-edited. As for the waveforms moving after slip-editing, it only happens when I manually move the waveforms of either (I'm not sure which) of the linked clip by Shift+Alt-dragging beforehand. I haven't really tried to reproduce the issue, so I usually just slip-edit the original clip first and then Ctrl-drag to create a linked clip.

Ok, I tried exactly the same editing shown in the first image using the Normal project template and got exactly the same result (the reflected gray edge moves to a wrong position and the waveforms move, too). This is definitely a bug. I suggest you report it via the Problem Report Form.

Happened for me at least in Dorchester too. In my case during multi-track comping. Kind of a show stopper, what if you don't notice right away and continue working for a while?