I've never seen a Bandit VI.
Now with due consideration for the preservation of all parameters, settings, ladder, etc, is there anything like a battery to power a CMOS chip? Removing said battery may kill absolutely everything, after which you would need to reload stuff. If the control uses a PLC ladder, maybe that file is protected with its own password, which would likely persist even after a reinstall.
I'd suggest making a call to Albright's cnc support services in Bozeman, MT. Len Albright might be familiar with this model.