What happens if you go to View menu > View using CPU?
I can't replicate the problem (with or without CPU), are you holding down shift when moving the mesh? Are you on the current CC, what OS, etc.?
Same wether I hold shift or not. It varies also depending on the size of the rectangle.
Latest os x and cc, macbook pro.
Hmm, truthfully I am stumped. I can't understand, especially if you are getting differnt results with different rectangle sizes. So it isn't just the one rectangle that you are having problems with. Does this happen with other shapes as well, like an ellipse for example?