surface now it's good, now it isn't

I downloaded an item from Traceparts in Solidworks format.

The ASM has 3 parts. Each part has 1 feature. 1 part has however a surface feature.

All's fine, no errors, no problems.

I used the ASM as a sub-ASM for several hours without an issue.

Then I come to the realisation that I have to move that sub-asm a few centimeters. Result is that the surface feature now has an error and no matter how I try to rebuilt it, reload it or restart SW or even the computer it keeps having a bunch of errors in it's surface feature. The reason being that it has safed the part in that state.

In the end I had to dig up the original file that I had downloaded and replace the troubling part. This time however I put it as read-only so that it doesn't overwrite it.

Anyone else ever seen something like this?

I would post the parts but I don't have them anymore.

SolidworksGeneral