On an HS Hydro, a 45 error is, ss info lost,aux door close contacts open. So you have a problem with with the Door Board. If I remember correctly that's where the aux contacts are located. A 45 error on a Miprom 21 is usually caused by a position error.

Not sure but they added a micro switch on the crank arm to keep from doors reversing and running with doors open. Know there was problems keeping adjusted properly.

Does unit still have the awful WG (Worm Gear) Door Operator? If not replaced with what?

Most HS Hydro's had the WG operator, a few had the 104 Board with a MAC operator. The micro your thinking of was added as a code requirement, it threw a 55 error on Miproms.

We battled this for months on an HS with the WG operator. That auxiliary close limit was put right on the strike and it was one of those heavy duty plunger switches that are threaded so you can flex right to them. If the car is sitting with no demand (no squeeze) and it comes off that switch dropping SS info, it shuts down throwing that fault. In our case the spring tension of that switch was just too strong and assisted too much pushing the door back open a little bit. I could adjust everything and get it to work but a couple days later it would be doing it again. Long term solution was to replace that switch with a lever type micro switch.

A 45 Error w/wg operator is an output from a relay on the wg board. New board.

Yep

I think California required an auxiliary door close switch external from the door board.

Yes, it has the WG operator. I will check on the aux door close switch. I'll let you know what I find.