Unable to Unlock a Member

I am unable to Unlock a Member record.
My site started out as v13.x and is up to v13.7.2 now.

I can edit the Member and set both Approved and Locked out to off (they show as grey then)
Save the record.
The Locked out setting immediately goes back to Locked, and the green bar appears.

The Approved setting is changed but the Locked out setting is not.
There are no Log messages relating to this action to show what might be going on behind the scenes.
This apparently was a problem way back with v8 or thereabouts and was apparently fixed, but I am seeing it here.

From what I can discover when searching, it is possible to unlock a member by going into the db directly but I would rather not have to do this as it is not a sustainable fix.

Is there any other option?