Thanks for posting the sketch offset issue and your data. I'm following up here to log a ticket for that behavior. (logged FUS-150219)
Regarding your question about the sketch, and not being able to constrain it, I found a ton of floating geometry.
Trim construction lines, delete them if they are not attached to anything, give sizes where indicated, and get rid of the text, it should fully constrain.
Hi,
I suspect that the behavior is caused by the direction reversal of the offsets.
As long as the changes are small, the sketch solver seems to ignore the reversal. For larger jumps, however, an error message appears.
Günther