The Probes had been programmed to sent all communications through communications platform. They have the ability to scan multiple channels and relay messages. They have long wave and FM radios and the antenna on the back of the probes would lay down for the trip to Mars. They were not programmed to talk to each other directly, Brace wanted to know what was being said between the probes so they were to send the communications through communications platform. If a probe was acting as a relay it was just to route the signal in one channel and out another without reading it. After reading the message from Zachary it looks like he read the one from Bette. It’s possible that now they are scanning all channels for input. It is also possible the antenna was bent down into it's shipping position from the cave. And that the other probe returned it into place. It’s should not have been stuck down and it has a rubber to protect them.
I don’t thank that he will always be relaying the messages but me may be reading them as they may all be reading each others ..
Dr.D