Had a failing HD in the pool. Wanted to replace it but couldn't remove it due to the above error. Tried several times, rebooted between attempts and no joy. Finally gave up and nuked the pool from orbit and started over. Fortunately the pool was backed up so I didn't loose anything. The new pool is x2, dunno if this will help me avoid this situation tho.
I know it is now too late but how should I handle this situation should it ever occur again?
PS: Yes, I told it to ignore errors and remove anyway and that had no effect.
TIA