Truma Ultraflow problem

Hi all. On my last 2 trips out I have had a problem with the water pump. It works fine for a day or so the play up, very intermittent  working. Its a truma Ultraflow surge damper with pressure switch. When I removed it I noticed the 'o' ring separating the water from the PCB was on it way and I could see water had seeped in and i assume that's when it starts playing up. Do you think changing the 'o' ring will sort the problem and it will work once its dried out or can I change it to a different system as these are obsolete now

Many thanks.   Alan