One of the unfortunate side effects of slow aircraft sales has been an erosion in the maintenance base. Many smaller shops have disappeared and some of those that remain are either losing the ability to do some kinds of work or are just declining to accept it.
One maintenance procedure on the chopping block has been the resealing or repair of wet wing fuel tanks, especially in Mooneys, but in a few other models as well. At best, repairing weeping wet-wing tanks is a dark art, at worst, it’s something some owners say they have to have done several times to stop the leaks, if even the leaks can be stopped.