HP-71B won't turn off when loop is broken

[Sylvain Cote]

Dave's suggestion is interesting.
My take, it's either that or the HP-IL interface internal registers are corrupted or in inconsistent states.
I would at least try Dave suggestion,
then if it's not working reset the interface (RESET HPIL, OFF IO, RESTORE IO)
then if it's still not working completely remove the interface from the 71, power cycle the computer then reinstall the interface.
Sylvain