In just this one assembly, after making a few changes, I receive the error \ "an unknown error occurred while accessing..." when trying to save an assembly. How do I fix this?
If I press Ok, the file does not save and I am back to square one. Also, the text in my dialogue box is different from your screenshot. Mine says, "an unknown error occurred while accessing {filename}".
I had the same problem it originate in some suppressed feature or sketch in one part, open parts in the ASSY one by one and try to save them, one of them should give you the same massage, then just deleted any suppressed unnecessary feature.
I have similar message every day c couple times per day.
Click OK and keep going.
SW 2017 SP 1, WIN 7