Trans. failsafe pgm mode

Trans. failsafe pgm mode.

BMW/540I/4 door seadan, Year 2002. Miles : 45699. I had problem with my car just 2 weeks back, heard noise on back of car and Trans.failsafe warning came on car screen. Took it to Runnak BMW service center in Thousand oaks. Charged me 732.89 for parts A. Trig.Contact (24-34-1-218-551)(Qty -1) B. Gasket (24-11-1-422-676)(Qty 1) C. 1/2 Ltr Trans oil (83-22-0-004-008) (Qty 10)

After all that fix, I had same problem afer a day, I took it back and now this time they said they fixed ohter sensor and did not charge me.

Question: I am not sure what they replaced as fix during my fist visit was really required?? Was that really the soultion for my reported problem. If so then why did I had same problem again after the fix.