When it starts happening one way to avoid it is to simply lock the unwanted clip. That way it won't get selected or moved without unlocking it again.
To do this select the clip you want to stay in place > Right Click > Lock > Pos/Data. You'll have to do it twice using right click. You can also lock clips by opening the Inspector (press I) > select the Clips tab at the top > click on Lock and select Pos/Data.
I've been doing this quite frequently to avoid the issue. In fact I lock ALL clips except the ones I'm currently editing because it can select across tracks and if this happens off screen it can really eat up a lot of time trying to fix the unwanted edits.
I thought that it was perhaps a constant bug but have recently noticed that it only happens after working with a project for a while so something is getting corrupted. It is the worst bug I've encountered in Sonar X2.
Cheers.