Fisher&Paykel wash-machine SOMETIMES does not centrifuge ?

I have F&P EcoSmart, top load machine. I bought it about 6 years ago and it was working like a Swiss clock till 4 weeks ago. All of the sudden it would randomly "choose" NOT to do last centrifuge in a cycle. Sometimes it drains the water and than stops (most of the time), sometimes water is in. Sometimes it drains, just starts to centrifuge for a sec, and than stops. When this happens , I have to repeat the whole cycle, sometimes COUPLE of times until it finally finish a cycle O-o !!! Sometimes I have to change a cycle for it to finish, sometimes I have to unplug it over and over until it chooses to centrifuge - I AM AT MY WITS END ! Than for day and days it works perfectly O_O !!!! I can not even call a repairman since it works great most of the time and he will think I am a "dufus" LOL
PLEASE HELP : ((((

PS: There is never too much suds or anything like that. I have this machine for 6 years, so I really know how to use it LOL ;)

Aleksandra
March 2011