I wouldn't mind getting a pile of those things that are all jacked up to work on and/or tinker with. Though I have no interest at all in purchasing them for a repair/resale thing here, as I'm only interested in the issues and how to solve them, if they can be.
Triggers that are always on could be a botched Trigger mod that left a solder bridge somewhere, or damaged a trace, or removed a component or even a bad Hall sensor. Given all those things are known to be good, then you're left with an MCU (Micro Controller Unit, the large black IC on the main board) issue and there's really nothing that can be done there without having access to the tools and software that were used to make the things.
Stuck buttons first thing to check is the traces and make sure there are no shorts or weird Resistance values to ground, as that's really about all that could cause that. If they are good then you're back to the MCU being the culprit and can't do much.
Sticks that move on their own are most likely just worn out. The PITA there is they seem to be calibrated after they are made, so installing new ones will have the same effect, or they may drift in the other direction or you might get lucky and they will be close enough. I started work on a PCB to correct that mess, but even it's a bit of work to install, but I have finally dug it back out to try and finish it up. On the flip side of that, if the Sticks are good and the problem is something else, then you're back to the MCU issue again.