central locking problems

can anybody help please..... fabia sdi 2002 the central locking seems to open and close while driving car,even locks all doors while parked and keys in ignition...but once locked and keys out of car remains locked.....sometimes boot does not open when u unlock the car..:confused: driving me mad left keys in ignition car locked itself had to go and get spare mechanic said it showed no fault codes??????? any info vey welcome thanks..