ST7000 Autopilot Problem - Randomly Steers Hard to Port

[phantomracer]

I am having an intermittant, but serious problem with my ST7000 autopilot.

At very random times, in either standby, auto, or track, the AP will go nuts - wheel goes hard port all the way, and I can't override it, and displays 'MANUAL' on the display! To fix it, I hit 'standby' to regain control of the boat.

I thought the 'manual' setting was to be able to override the steering from auto in an emergency. This setting is 'off' now.

There seems to be no consistancy when it happens.

Not sure if this is an environmental issue, ie stray energy from radar, etc from other boats, land based communications, etc. two times it happened in the Cape Cod Canal, which has a lot of high power stations. Was just a wild guess. But it has happened in open water as well.

The electronics system on board has a NMEA fluxgate compass (not the original), Lowance chartplotter/gps, AIS receiver, tridata instruments, feeding into a Brookhouse multiplexer. Not overly complicated. I also have a SPOT satellite messenger on board. Not sure if that could cause issues.
But it is disconcerning that I lose total control at random times.

Overall it is working great, other than these random emergencies!

Any help would be great