Hi Nick,
I tested the file and unfortunately, it is filled with zeros only so nothing we can do on our end (we don’t store users' diagrams nor can restore this one due missing info)
We had a couple of similar reports earlier but we fixed the issue in 12.3.2 version so not sure why you experienced it: Non-empty files filled with zerosBUG
Could you check if you able to find ~${FILENAME}.bkp in the system?
Do you see older versions of the file when you right mouse click the file > Properties > Previous versions?
Regards,