A lot of the problems come from field built jumpers. I'm sure that on occasion you'll find a factory made one not pass a PIM test, and then the blame game begins where everybody wants to be compensated for lost time and materials. Torque a connector too little or too much and you'll see the same problem. Sometimes you inherit the problem as well from a previous installation. A slightly scratched or dented DIN is sometimes the problem. With too many components in the RF path, I think that there needs to be more training for everyone on all levels. PIM is a real problem and is going to get worse over time as systems degrade by the elements and equipment collocations.