[Richard]

What is possible and frequently observed is that the push on tubing connections that Newell is fond of using, leak at a much higher rate in colder weather.

As far as the pressure switch leaking, anything is possible.

I would take a very close look at the Newell provided water separator/filter used with the aux compressor. They are prone to porosity.

And of course, the clearances in the pump will be much looser in cold temps, the pump may be approaching it's useful life.

Diagnostics in order. Deadhead the pump against a gauge and see what it's capability is at cold temp before you throw money at a new pump. Then soapy bubbles. Playing with water at freezing temps is always fun.