Solved! Go to Solution.
Solved by nestly2. Go to Solution.
It shouldn't switch to PSpace on it's own, could you be double-clicking outside of the viewports(s)?
An easy way to tell when it happens is while in PaperSpace, change the VP Color of your Dimension layer to a color you'd never use for dimensions. Now when a Dim is placed in PSpace, you'll notice it immediately.
Excellent tip, Nestly! I can attest to the same behavior happening on my install of AutoCAD 2013, and I suspect it is tied to zooming inside a locked viewport...