I know you said you changed the hall button interface...Was that on both cars?

I had a similar problem a while back on an LRS3 duplex. I changed the interface board on the car I shut down which allowed calls to latch again.

I have also heard of this dispatching issue if the wrong car is turned on first on LRV3's. Did you try powering down both cars, turning the right car on then the left?

I had this problem before.same situation..went through all the motions with sending one car up to the top floor shutting one down,followed by resetting the first car waiting several minutes to turn the next car on..changed out both hall button interface boards..logic power supply in suspected car..but nothing corrected the problem until we replaced the 1k pull down resister in the lead car to a 750ohm.this prevented the 24vt logic for the cpu to operate properly.under extreme conditions, car calls,etc.kept the processor from clipping..

Wow, guys, thanks. Did not try sequencing the power. Thanks, I'll try it. And the pull up resistor sounds like a great idea too. Thnaks.

Yep, turned one on first, then the other, now they talk just fine.
Thanks!

Wow, what a strange solution to the problem...good to know.

save that one ..it also works on my mph 1 and mph2...proper sequence starting....if not I get fire service or other odd things