Flex 6500 Relay "Ticking"

Evening all. Bit of an odd issue with a 6500. It's running 3.2.39 (this issue started when running .34). It happens whether SmartSDR is running or not, the radio just has to be booted.

A relay is energising about every five seconds, then (it sounds like) de-energising about a second later. If SmartSDR is running, it carries on in both transmit and receive. There's no noticeable effect on the operation of the radio. I run the radio with the ATU disabled. No other devices are connected via CAT.

Any ideas?