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»someone installed it trying to fix some other problem«

over the years; well designed properly working go astray…..

pumps are sold by well meaning hungry folk.

I believe there is a square d float switch with a box that looks like a pumptrol.

Check valve in the discharge line would be my first guess.

If that thing is triggered by a float switch in the receiver, I'd agree with @mattmia2 up there — a small leak in the check valve coming back from the boiler. But wait… there's more! Is there a way to adjust the differential between on and off on whatever triggers it? That could also be a problem — whether it's a condensate return (switch in the tank) or a boiler feed (switch in the boiler).

very strong possibility it doesn't need it and someone installed it trying to fix some other problem.

The first thing to look at is what controls the pump in the feeder.

A missing or failed check valve could cause the condensate to drain out of the boiler and back in to the tank every time the pump shuts off or various arrangements that need some sort of a vacuum breaker or equalizer so they form a syphon.