We also have the 17.56-2 and have also had a water leak from the bathroom where the silicon around the toilet and the inside wall was only a very thin application and it had not sealed, hence the water from showers had run down the inside of the wall, along the lino and out into the main van area. This is now a warranty job...
The other concern I have always had is that if the water inlets (mains or tank fillers) leak, as all the electrics are in the same place (under the dinette seat), then there is a chance of major electrical damage to batteries, inverters, Setek, etc.
Will certainly be adding tape and tighten the nut and add to the regular maintenance programme!
Thanks for the heads-up!
Cheers,
Rohan