Probably the biggest precaution is potting pickups with plastic bobbins for too long in too hot of a wax solution. Pickups need to be agitated quickly as they are submerged in a wax solution and should be done by a qualified repairman. Using hot wax can be very dangerous and should not be done especially on a home stove.

There are products designed specially for wax potting and with control temperatures and instructions. Leaving a pickup in a hot wax for too long can cause the pickup to melt and distort. The coil winding is under much tension and as the bobbin heats, the coil wants to squeeze the inner walls of the pickups and can change the pole spacing and tolerances in the pickup. Please let the qualified repairman do it and he will be responsible for the product.