looking for a lil help with a TXR5 loosing communication with rear GAL MOVFR DO.

Front doors are fine address 01 (i/o's all Green on CADI) but my rear doors address 07 intermittently go from all Green to all Red and will literally disappear from the SMLCD screen.

Multi conductor carries signals from both DO's to COP and connect to 2 SPIO boards then signal is return to controller through LON.
Before thinking it through I had already ordered SPIO boards of course replacing them didn't help.(I never loose communication with my front DO).
I'm thinking DO board is flaky but what gets me is all DO board LEDs function as they should when doors are operated. I will meter input signals at SPIO board tomorrow to see what it looks like.

-Getting 208 faults with 05 extra info: communication or power failure

It's a long 3.5 hour drive to this job so any help is much appreciated

Thanks

Update:

Rookie mistake...I completely overlooked the car top junction box where both DO's are wired into LON16 boards. After resetting service pin elev ran over 400 trips with no faults.