I put a piece of material approximately 9" x 12" in the GF and then loaded a file that included a 9" x 12" rectangle as a positioning guide for some a grid I was scoring. The loaded rectangle was about 1/2" larger than the material in both dimensions.
I assumed that I had a sizing issue with the loaded file but after two or three iterations of fixes that had worked in the past for that issue failed I used the loaded artwork as a cursor to check the material size.
You guessed it, the material measured about 1/2" smaller than I knew it was.
I cycled power on the GF and the issue was cleared.
Refreshing the browser window might also have cleared the issue, but it wasn’t the first thing I thought to try.