Hey, kids. I'd be most grateful if one of you can point me in the right direction. I've been working on this for a couple weeks, and I'm out of ideas.

Symptoms from inside the car:
Running normally, come to a floor, door opens, door closes. Immediately the annunciator reports "We are experiencing technical difficulties." All car calls drop. After between 5-15 seconds, the car will once again take car calls and all is well. The elevator can go for a day, or sometimes the symptom occurs after 10-20 runs.

The problem occurs in both up and down directions. It also occurs after I've taken the car out of the group and turned off door operation.

Symptoms from the machine room:
Everything is running normally, and then all of a sudden in will go to NAV. After a few seconds, it will go back to NOR. The MCSS faults show a 2700 and a 2702. However, the brake is not the cause, but that's the first thing the computer picks up. Those are the ONLY two faults, and they occur EVERY time this event happens. What I DON'T get is a U or a D. They turn on through the MCB board, but I don't know what happens prior to that, to turn on the XU and XD signals. I can see that they're turned on by modules on the board, but that's it.

What I've tried:
I've replaced the MCB with one from Otis. I've replaced all the relays that turn on with the self check (CIO?). And today I replaced the Ring Board.

Any ideas what direction I can take this on Monday morning? I can go 150 runs with everything ok, and then all of a sudden I'll fail to get the XU or XD from the MCB. I'm stumped.

Thanks.