flm hybrids problem

[RUSTED]

ok now i shimmed everything and everything is running fine except 1 thing , ive ran it twice till now , and the rear drive cup gets loose every minute , i even put thread lock on it it still gets loose , ive stripped 3 grub screws till now , how can i stop it from getting loose ??? btw im using the duratrax raze cups



and the front rpm arms ot damaged , should i replace them with flm arms ???