I had my Navnet shutting down with the diruptor fuseĀ every 1-2 hours. I checked the Navnet. The Black Box (under the seat) is hot, but it was always hot. ( about 60 degree celsius). I opened the top of the Navnet Blackbox and all fan's where working.
So I changed the diruptor fuse on the panel (NAVNET). The diruptor fuse is: Code 7122104 16D (16Amp).
Now all is working fine. Just in case someone has the same problem.