My touchpad felt laggy and jumpy on my Lenovo Yoga 7 after a week i bought it. It starts with finger rubbing and it is not OS related doesnt go away if i dont press to hard on it to make it contact with something on the body and release the static energy. I opened up the laptop and observed the issue and its grounding problem.
Notice on the above picture on the left side there is squishy conductor, its almost went deep inside and doesnt make contact with touchpad. I tried poking it with screwdriver to reform to its original shape. This fixed problem but after couple days it looses that squishy form again and problem starts again. I added aluminium foil to right one, i made a bit thicker where it contacts squishy thing so when touchpad screwed in to place it should contact.
As a fail safe i also added some more grounding with aluminium foil to the touchpad itself. There was a copper place on the pcb(where i put tape over you cant see) foil touches there and goes to upper metal. I didnt want to solder because i think if not done correctly heat would mess up surface of touchpad and will cause bump.
I measured with multimeter and it seemed ok. I have been using like this for over 4 months and no issue since.
As a bonus i noticed metal body that clicks on touchpad button doesnt contact directly because of design choice it doesnt reach so they added some acrylic tiny plastic to make it reach to button. And this does make loud clicking noise which i am not a big fan of. That acrylic piece hold in place with double sided regular tape, i removed that and added double sided soft/foam tape like this:
This made touchpad clicking mushy, if you like clicky switches on your keyboard and mouse you may not like it but its silent now. I think instead of foam tape some lube can be added for better result but because foam is thicker than regular double sided tape it shortened(to almost none) the travel distance so touchpad doesnt go that much deep in when clicking and i am happy with that.