There should not be water in the pressure switch. Whether there's damage in the pump head housing, a bad membrane, a "manufacturing issue", or possibly freeze damage from incorrect winterization of the pump ???? It's anybody's best guess.
The pump is warrantied by FloJet for (I believe) 2 years, so if your trailer was bought new and less than 2 years ago, you might contact FloJet and discuss a warranty replacement. If it's not in warranty, you can buy a pump head/pressure switch assembly for around $50. If you buy the pump head and (who really knows at this point) if the pump motor may also have had some leakage into it, then it's possible that replacing the pump head/pressure switch might result in the need to "then replace the motor"...
That said, a new pump at Amazon is only $54, so it seems "counterproductive" to not just buy a complete new pump assembly and do the "plug and play replacement"....
https://www.amazon.com/gp/offer-list...&condition=new