Checked the 409 relay and fuses also checked fuel pump and fuel filter and their ok

Since buying my jetta i have had nothing but problems, one of the worst being a split in the top of the fuel tank my mechanic tells me from what he can see he believes its a manufacturing problem and to add to it the original fuel filter was still on the car at a 100,000 kms has anybody else had problems with their fuel tank? As vw tell us not their problem but cant understand how i could possible do that kinda damage to the TOP of a fuel tank thanks in advance