Well, I found that the bolts which hold the pallets to the heat sink assembly will over time loosen a bot. I suspect this is due toi dissimilar metals (Copper pallet, steel bolt, aluminum heat sink) having different expoansion rates. Old VWs had spoecial compensating washers under the head bolts to keep this at bay. The Z series modules have you to tighten the pallet bolts about twice a year. They're hot pluggable, it takes maybe twenty mninutes to do a Z-10.