Unstable models surfaces

I get this problem every now and then with imported parts. Normally have to reload or redo some work.

In this case I have redrawn the part because it had fallen over and then erased the original imported file.

So it’s a Zw3d model now, after programming it had happened again. In this case I can roll back the design tree and regen each feature to get my work back.

Are others having this problem, any solutions?Plate

Hi Matt,
send me your model… Doesn’t seem right.
In my experience if it is not a bug, i is a modelling glitch.