condensate trap overflow...fixable?

SeeBuyFly

Hi...we have a 5-year-old HTP Elite FT boiler. The condensate trap is overflowing occasionally, and water is running out of the top where it connects to the metal drain pipe and is held with a clip.

I cleaned it (although it was not dirty) and put it back. It worked for a while, then overflowed again. Just holding it under a trickle of water in a sink, it works fine 9 times out of 10 (water comes out the side tube), but 1 time out of 10 it overflows with no water out the side tube.

I assume the float is not always moving freely, but I admit I don't understand fully how this thing works.

Is this a problem with a possible fix, or should I get a new trap (not exactly cheap at $67 for a plastic part)?

Many thanks for any help from the experts on this forum!