Heater matts on Fresh water tank

When out over the weekend the rubber style heater matts on the bottom of the fresh water tank fell down.
I see there were just glued up this appears to have failed. So had some double sided tape in the van so stuck it back up with this and cable ties. 
Now has anyone else had this happen and how did they fix it for a permanent fix.  I asked the dealer they use tank tape.
As I would think they should be bonded for the heater Matt to work if there is an air gap it would not work.
Any thoughts on the this as the van is only six months old.

Campbell

Impact adhesive would be my suggestion.

It cures to a hard rubberised finish and if you've ever tried to clean any off a surface you will know how tenacious it is.

Hi this happened to our Warwick xl on our 1st trip on both tanks went back to the dealers to be fixed along with the water level indicator (waste) not working we got the van back 1st trip out (to mallorca) still here happened again so taped up till we get back ! Also noted that one of the blankets seems to now only cover 1/4 of the tank