PGXL v3.7.28 Unusable, Firmware SWR Failure in SSB. Reverted to 3.7.18

I upgraded my PGXL to v3.7.28 and everything appeared normal at first using a steady test signal from the Tune button. Even at full power the indicated SWR remained steady and low. However in SSB, the indicated SWR would hop around greatly at a regular interval of about one second with normal voice modulation, possibly while the firmware recomputed it. At excessive indicated SWR values the amp would trip giving the excessive SWR firmware fault reduring the amp unusable in this mode.

The setup is a 6700 feeding the PGXL and then into TGXL and Antenna Genius before the antenna. During the problem, the TGXL indicated consistent low SWR with no abnormal fluctuation. The problem was duplicated on 75M, 40M, and 20M using separate antennas.

I reverted the software/firmware to the previously successful 3.7.11/3.7.18 test versions to regain amplifier functionality. Amplifier is now SSB usable again.

Anyone else with this problem?

73, Bill AB7AA