fyi.
I don't actually repair units and don't remember ever seeing a unit with a bad touchpad, so not sure how likely this is, but remember hearing some customers running into issues with bad (keyboard?) FFC cables as well which probably would not happen if you were not disassembling the unit and re-connecting the cable very often.
If you haven't inspected the touchpad FFC cable, make sure everything looks good there and assume the plastic clips to hold the touchpad cable on both the motherboard and touchpad side look good as well.
Also, the notebook keyboard and touchpad may be related some, so more serious keyboard problems might affect the touchpad, but probably not very often.
Anyway, just wanted to run this by you as well. thanks.