Did you check the actual voltage at the batteries? Something is wrong with that controller if the voltage is correct. How many AMPS are you cooking those batteries with?

My guess is that, if it's only .01 amps, maybe your batteries may survive. If you're cooking them with some amps, then I'd not keep that charger connected until you fix or replace it.

Our Lifeline AGM's float at 13.9 volts, for example.

Have you tried to turn the unit off and on? Have you checked the set-up was compromised to see if something is amiss? You might go to the default set-up and see if resets.

I'd call the manufacturer and find-out any suggestions they have.

I don't know how it bleeds off the solar cells output.