Hi, I'm trying to thicken the main car surface which knitted together as a single surface.

However when trying to knit by enter a value as small as 1 mm, the full previous shows up and solid works takes a minute a so to think about it but then goes back to the thicken feature without the thickened feature applied and no error shown. It just does this again and again if I apply the ok (green tick again).

I've tried selection and deselecting the merge result to no success.

What am I doing wrong?

I can't attach the file here because the file is too large at 28.9 MB.