The top topic in this forum is now sticky and contains the latest version.
Which pocket are you using? Is it possible you have some condition set that is making the code run a long time- like asking for 10" deep in .001" increments?
The only reason you could not return from the preview is if Mach is still processing the code, as it does before a preview. Maybe you have found an infinite loop, cut rectangle had one, that was the fix in V2.85
Can you post a screen shot of teh wizard with all the DRos filled in?