Seems many have this issue. Me too. But I got to find my issue to be a glitchy connection of the trackpad cable. So I have now added extra padding to the shield to make it firmly pressed towards the motherboard. And keyboard and trackpad is working once again.
So basically follow this guide
https://www.youtube.com/watch?v=FzcBL1NBtik
See the shield in the middle of the motherboard, That is the one that needs extra padding to press down (or up when you turn the computer around).