Ok , had that on my 2006 Bav30 also. What i discovered was the hot water cylinder/heater pipe fittings began to leak, im talking about the plastic push fittings. The problem was the heater heated to above 65c, it was nearer 90c! the fittings used by Bavaria are only rated to 64C, but the thermostat was set fully on! not a Bav fault, more to do with the commissioning brokers failed to check settings before handing the boat over.
So after a few years the fittings start to fail and leak, i took all the fitting off close to the heater and replaced with new from Plumbase, cheap as chipps and pushed everything back together, before using i adjusted the heater down to about 50c, which saved elec, and the problem didnt return in the two years i kept the yacht. The only other thing i did was to move the first fitting away from the heater/tank by about another 3inch, which reduce the temp of the brass fitting effecting the plastic fitting.
Good luck