I had a similar problem many years ago, where a 20 watt 146MHz transceiver, when keyed to transmit, made the metered input 12volts rise quite considerably, when used on a home made PSU. I assumed this was due to my home made power supply's metering curcuit, or the regulator itself being sensitive to the RF signal. I never worried about nor persued the cause, just used a different PSU. By the way my PSU's max output voltage was only about 18volts. I think the metering may have indictated the max output. It was a long time ago!
Your effect may be due to a similar cause. That is RF getting into the PSU. If it's affecting the PSU regulator you may be in risk of damaging the pa.
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