Redundancy checks I think were like the newer version end of run check. I would first start with the battery, then I would verify if this happens everywhere in the hoistway, or just in at a single floor. I heard stories back in the day, of gate, DCL, and hoistway interlocks being too close in sequence and making that 16 bit processor cry. Remember the TAC 20 fault codes famously led you down evil and dark paths that had absolutely nothing to do with original problem. If this happens everywhere it could be a simple corrupt door scan, and with a new learn travel, fixes itself. My money is still on the battery though.

*Edit* read what you had for the failure in the open for the advanced. Very possible the relays at the bottom of the board are bad as this is a monitor (typically a back contact) fault. I do not have a unit anywhere near me, but check the relays K7-12 I think, if they are blue finders, replace them all. If it's a DC Finder relay anywhere on the board I replace them, even before checking the battery, that's how horrible they were, and how far into the woods they would take you. The AC relays always seemed to work very well.