MacBook Pro trackpad keeps going faulty. on my 3rd one

i have a 2011 mb pro and about 8 months ago the trackpad became erratic and unresponsive. Checked all the obvious and couldn't see anything. No spills. Battery ok. Swapped the trackpad with brand new one. All good for about 4 weeks then it happened again. cursor has a mind of its own so I have to use magic mouse instead. swapped that thinking it was a faulty unit and the same had happened again. Brand new trackpad now going mental after 4-5 weeks use. The mac never leaves my house and is not heavily used. What am I missing? Any help appreciated.

RIch