I had this problem from a single drop of soda that managed to fall in the crack between the touchpad and case.
I took out the touchpad and but was unsuccessful in getting the touchpad itself apart. There's 4 tiny retention clips holding it together that were giving me trouble.
I instead submerged it partially in isopropyl alcohol, let it fill, drained it, repeat. After a few times I dried it off, used compressed air to blow out any remaining internal moisture, then reinstalled.
Worked like new.