Intermittent problems are the worst to troubleshoot. I assume this problem just started happening. Here are some generic ideas to eliminate possibilities;

- Is the push to talk switch intermittent and while bouncing around in a thermal you are effectively not transmitting part of the time? Clue: does it also happen on the ground without bouncing?
- Microphone can also become intermittent while bouncing around in the air.
- Try replacing your battery with another from a friend (lithium would be best). Even though you said you had a fully charged battery, transmitting is the heaviest current use you have (except maybe a transponder) and if the battery voltage droops too much it can stop transmitting. Then the voltage rebounds and you start transmitting again. Repeat ad infinitum.
- Is it interference? Shut off all other avionics, varios, etc.
- Antenna? Temporarily replace the glider's antenna with a portable's "rubber duckie" antenna. If the glider's antenna is bad check or replace the BNC connector as a first step.

Anyone else have some troubleshooting tips?

Ultimately, you may need to send the transceiver to a shop for a bench test.. Make sure they know Beckers and that you tell them about your symptoms. Good luck. Report back!