Bench update stuck on db migrate

I am running a bench update but the process appears to be stuck on this part…
CPU is sitting at ~60% (not a particularly powerful machine, but anyway) for ~30mins.
The update is minor (9.2.15 → 9.2.18). I am loath to interrupt it, just in case, but if anyone has seen this error and has a tip…

If not I will interrupt it and rerun the migrate (unless otherwise advised)

I manually altered the db and changed values in due_date from NULL to ‘’ (blanks) using
UPDATE tabGL Entry SET due_date = ‘’
and the update now processes successfully