In case this helps, we have had a similar problem with our brand new Swift Sprite Alpine 2 2024 caravan, and have managed to solve it. The pump still makes a little bit of noise, but much much less than it was doing.
This is our first caravan with an internal water pump, so feared it was normal, especially as some folk say they are a bit noisy anyway. But this was way beyond "a bit noisy". Like a road drill under the bed at night - really! Hammering through the caravan's bodywork.
Swift's persistent advise was to alter the pressure switch setting on the pump, which was completely inappropriate. Changing the pressure at which the pump turns off is no use at all when the noise only occurs while the pump is running. Like taking your car to the garage because it is makes a horrible noise whenever the car is moving, and being told to stop the car sooner!
The problem was that the water inlet pipe feeds into a hard plastic elbow fitting, before it goes into the pump, and this elbow fitting was up against the wooden bulkhead the pump is mounted to. As the pump moved on its flexible mountings (as it is meant to) it was hammering this plastic elbow fitting onto the bulkhead, which was very loud. I could reproduce the same noise by just gently wiggling the pump on its mountings by hand. The bulkhead acts as a soundboard and amplifies the noise. So I fixed that by re-routing the inlet pipe so the elbow is now positioned away from the bulkhead. No more road drill noise.
But I also then realised there was a really annoying whine/hum, and so I ran the pump detached from the bulkhead, just held in my hand, and the noise stopped. The noise reappeared when positioned onto the bulkhead, even before its rubber mountings made contact. Turned out to be due to how Swift have routed the wiring for the pump, between the pump body and the bulkhead. The pump's flexible rubber mountings can only damp out the noise so long a there is no other acoustic connection between pump and bulkhead, but with the cables jammed in between, the motor noise was transmitting directly to the bulkhead! I fixed this by using 1/2" rubber tap washers (which are about 4mm thick) between the rubber mounting feet and the bulkhead, with longer screws, so none of the wiring then jammed between.
Really disappointed with Swift on this. People have been complaining about this for 10 years or more it seems, and it is really just a simple bit of production engineering and/or quality control to sort it for people. Either Swift's production drawings are wrong and they need to sort, or they are correct but not being followed correctly by their production staff.
And as for the stock response of telling people to adjust the pressure switch - that just demonstrates a total lack of comprehension of the issue.