Edit: It worked! Took me no more than 10 minutes and the controller is working like new!
Hey guys, I’d been searching on and off for a month for a solution to this on my first gen controller and finally found someone who had solved it. See the final reply to this post: https://community.eu.playstation.com/t5/...
Essentially, install a new PCB circuit board. They are $6-7 on ebay (there are cheaper ones from China but I don’t trust those based on previous experiences); just make sure you get the right one for your model. From all I can tell, gen 1/2 used one pattern and gen 3 used another—seems to be a matter of where the contact points are for the motherboard.
I’d already tried cleaning the parts and looking for any corroded contacts or circuitry, but everything was in great shape.
Just ordered my PCB and will be trying it out Saturday when it gets here. Install is super easy; no soldering involved. Just pop the old one off the mounting points and out of the slots under the triggers/bumpers and slip the new one in. The PS4 controllers are extremely friendly to DIY fixes and cleaning. Awesome video instruction for taking the controller apart here, even though it doesn’t include disassembly of the PCB: https://www.youtube.com/watch?v=6pw2UMop...