Ctrl+z?

CTRL+Z doesnt work in sometimes, for example when i do Align surface then i cant back it.Why this happens?

That sounds like your surface went behind the camera. When the surface tool comes too close to the front of your view, mocha experiences a calculation error and this can make it hard to undo because the program is experiencing a math error.

Make sure the surface isn’t tilting too much and try again.

Cheers,
Mary

actually when click the Align surface not surface “Grid 8X8” becomes on my whole view window