The same model sliced with Slic3r RC2 and RC3. I think a bug might have slipped in there. 
on left rc2?
Yep.
Sure it’s not some mechanical failure on X (or Z) ?
RC3 works good for me - no issues.
it looks like what @Hans_Franke mentioned. X or Y belt or motor slip.
Slippage is a possibility, but it doesn’t explain why the bottom layers are so thin even though they are the right shape.
I’ve gotten an error when using slicing profiles from earlier versions. Try making a new profile and duplicate your settings manually.
I’ve had RC3 mangle some stls of mine and I’m not sure why. I’ve been using kisslicer instead.
Hmm. There is definitely something wrong with RC3. I just sliced another model and the gcode crashes my printer. RC2 code is printing fine.
can attach gcode from rc2 and rc3 from same item?