Broadway EB 2016 Fresh water problem.

We are touring in Ireland with our Broadway and loving every minute. 
At the start of the holiday the fresh water pump ran continuously when the pump was switched on at the controls panel. Presumably the pressure switch has failed. 
That wasn’t a problem as we switched it on an off as required however in the last couple of days the pump has stopped working all together. 
What is odd is that the control panel shows that we have around 75% in the tank but as soon as the pump switch is pressed the water level shows zero!
It reads OK once the pump is switched off.
I was wondering if the pump has seized and drawing too much current? The fuses are OK by the way.
I would appreciated any advice to what is going on. 
PS the van is going back to Marquis in Poole on Sep 9th for habitation check and luckily the pump is still under warranty. 
Paul

Difficult to diagnose a problem of this type at a distance, but my first suspect would be a bad earth connection somewhere in the pump circuit and related equipment.

As soon as we returned from holiday the van went back to the dealer for a habitation check and to sort out the fresh water problems. They were unable to repair the problem saying that the Sergeant unit needs to be replaced. I am waiting for a date for the replacement. I also had an issue with the waste water indicator showing full when completely empty. They say that the grey water tank needs flushing to clean the contacts which I am about to do. 
Paul