Phoenix IP43 3/50/12v switching to high voltage

Hi; I have a Victron Phoenix 50/3/12v charger for charging my 2 isolated 8D FLA batteries and Grp 24 SLA gen battery. Used only while on shore power AC. I have a smart sense on each and networked all to my Cerbo.

Every once in a while the charger goes sort of crazy overcharging one or more of the 8Ds, even though its fully charged. Shows it’s on Float at 16 volts! I came down yesterday to find one of the 8Ds at 128°F and charging for hours at 35 amps. Off gassing like crazy. It tested fine the next day.

The charger has done this a few times since I bought it a few months ago for no apparent reason. Turning it off/on when stuck in this output has no effect. However if I reset it to defaults and it will work for quite a while again before it repeats. It’s set to Normal mode. Recondition is off.

Bad unit? Anything else I should check or change on settings?

TIA, Jack