This error got me thinking about the file system. If this problem is fixable,
It is ! ! 
That would be great, but there’s still the question whether the calibration will survive the recovery.
If it doesn’t, then it might become less useful, certainly regarding the level of precision it had and the use I made of it. I think we’ll have to see. Maybe there’s a procedure to create a copy of the calibration data?
Maybe it can boot from the usb, without altering anything so the procedure can be run even in the stuck boot situation?