The problem cropped up again this morning.
Note the 1" dimensions at the upper right corner of this window:
See how they have suddenly become corrupted and gone off into space here. It hasn’t been edited. As in the example in my initial post, something makes the dimension vulnerable to an unknown cause of corruption:
Maybe forensics on the file will identify the problem with these dimensions by comparing the pre and post corruption 3dm files below. This has been a persistent issue. A dimension could disappear from a drawing and cause serious construction problems.
Page3aPreSproing.3dm (3.6 MB)
Page3aPostSproing.3dm (3.1 MB)