Hi, it's a DMC duplex. Occasionally the hall buttons fail to register. Also, when both cars are in service the hall button fails to reopen the elevator door at that floor.
For example:
Car 1 is at the bottom floor with car 2 on hand. Car 1 opens its door for a passenger and as the door closes the hall button reopens like it is supposed to. The situation work the same way if Car 1 is on hand and car @ is in auto.
However, when both cars are in service and I press the bottom floor hall button one car will arrive, but when the doors begin to close the ha;ll button does not reopen the cars doors. The hall button will stay lit and the other car will arrive.
We have looked through all the parameters and tried both cars as slave at the same time (disastrous), both cars set as master at the same time (disastrous) and we have tried both as master individually while the other is slave.
Figured I would see what you guys though of this issue.

One car should be Master and one Slave.. if This is set correctly try reversing Master and Slave cars and test it.

check you clc parameters car 1 is always the master ooo,car2 is the first slave 001,and if you have a third car in the bank it is designated as a 2nd slave oo2..