I am trying to repair a 10 year old Trane Summit BCU panel with 3 communication trunks. Two of the three trunks work fine but the third trunk we can old see about 1/2 of the devices. There doesn't appear to be any rime or reason as to which devices we can communicate with because we will see 5 unit vents, then not be able to see 2 unit vents, then we can see the next 2 unit vents. The system has Summit version 17.00.0053 SP1 software and the effected trunk has 33 unit ventilators (VUVC7511BODE) and 4 UPCM's on it.
Any suggestions on what to try? We have already tried resetting the BCU, turning off all the devices on the trunk and turning them back on, bringing one devise at a a time online. This all started happening during a week where there were tons and tons of thunderstorms.