I ran into this strange Xbox One controller issue on my PC, and resolved it, so I want to record it here because when I was looking for solutions, I found nothing similar to it on the Internet.
The problem was that the right and left triggers, even though I was pushing them all the way down, would only provide partial input. I found a site to test controller performance, here https://gamepad-tester.com and found that what was really happening was that when I pushed the right trigger all the way down, it would stutter a lot and only max out at around 80% to sometimes as low as 30% of the trigger, whereas when I pushed the left trigger all the way down, it would, weirdly, activate all the way, but also activate 20% to up to 60% of the right trigger at the same time, essentially cancelling it out. I thought this was a USB issue because I had an old controller where the left stick had gone off center, and it had the same issue.
Eventually just to try anything to fix it, I blew hard in to the hold at the top of the controller where the USB chord plugs into it. I did this a few times, blowing one time very hard (almost getting some saliva into it), and when I plugged it in, it suddenly worked, to my utter disbelief.
Anyway, future human, if you run into this problem, where the right and left trigger don't activate all the way even when you push them down completely, this may be the issue, and blowing into the USB cable connection, if it exists, may be the solution.
Update: About 6 months later, the issue was getting worse and worse, to the point where I'd have to blow into the top every minute or so to get the trigger to work, and even then the solution didn't work every time. I gave up and bought a new controller :(
