Never seen this fault in mine or in any I've installed. I'd bet it's a fault in the EchoCharger, though, and possibly one which was caused externally -- water
or foreign body entering the enclosure.
The Magnum ME-SBC is a very cute little device with some nice features. However, it's NOT the same thing at all as an EchoCharge which is a voltage follower device. Rather, it's a combiner
with permits two-way flow of current....set points and all.
I'd open up the EchoCharge and, if you see nothing evident, replace it with another. Be sure to install it in a protected location.