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.

Thanks for info but this is what is happening after spending more time on it.
Found out its a 2051 Door fault, which is loose belts. Belts are Not loose. 2051 Door fault comes up as doors get fully open.
Did adjust belts slightly with more tension. Car is running now, but still getting the 2051 door fault, however, it is Not shutting the car down now for some reason.

I don't remember having a sensor for loose belts, just that they could be indicative of a different fault... Let me check on this 2051 fault and get back at you.

One other important piece of info.
If you hold back slightly on car door as its opening, Door Fault does Not occur.

is this a closed loop or a linear operator. sound like you have a ibgt hard fault and it needs to be reset by the tool.

Eastern,
I think you answered your own question in your last post. You did say, "Belts", so I guess it's a late model HD operator. If so, It's a timing issue. I believe the controller has to see (in the open cycle); OFF of DCL first, then HWIL then GL, but the timing can't be all bunched up. That's why you can hold the fault back by manually stalling the operator for a moment. You're artificially creating a greater time lag between these three inputs. Either change the door open adjustment like "Open Backlash Time", or visually check the sequence of DCL, GL, HWIL to make sure the locks aren't opening before or at the same time DCL goes away. Could simply be a limit collar adjustment.

One more thought to add to the pile. Make sure you aren't getting a mechanical bind when the doors are completely open. Maybe a Door Gibb or something simple like that.

elmcannic, I did reduce the Open High Speed, and added tension to operator belts which did keep the car from shutting down.
However, the fault still appears, but oddly does not shut down.
Not sure how it can go from shutting the car down, to not shutting it down with the same Door Operator Fault appearing.
I did not adjust "Open Backlash Time", but can try that tomorrow.
One other piece of info, not sure if it matters, is that this is a Service Car, with a very high Cab ceiling. Therefore operator arms are very long.

john jay. I dont see a mechanical bind causing the problem as if you hold back on the car doors, fault does not appear.
It actually seems to be the exact opposite of a bind.

I still believe it is a timing issue. The collars have been known to slip on HD operators, I believe you probably have an HD 03 or HD 04. I used to set my gate on the hairy side of just making up, then bump it a tiny bit more so service geeks wouldn't yell at me for nuisance calls. DCL was done by closing door onto the stop, setting it, opening the doors a cpl inches, then using the manual door close button on the UDC til I saw the LED light on the board for DCL, verify no more door movement in the close. 1/4 gap between main dove tail of the clutch and pickup roller gave just enough clearance so the sequence of events could occur, and the CPU had time to see everything.

When I was reading the 2051 fault code, that's what I meant by it being indicative of a different problem. Had those collars slip more that once on me...still a little miffed on the redundancy fault, as I never had it happen to me. Perhaps the overall door scan has become muddled. I know if I move a limit or a parameter too much it's worth doing a quick learn travel just to make sure life is good.

how do you do a learn travel?

if you have a very aggressive accel and decel, the operator will fault too because the belt slips a little and when it sees DCL, the count doesnt match. Also, customers holding doors a lot will cause same issue.