Why is my touchpad sometimes drifting/disconnecting?

I have a blue DualSense controller that I bought secondhand off of eBay for a good price. It came in the original packaging and everything, and I couldn't discern anything wrong with it, playing titles like Astro's Playroom and Horizon: Forbidden West with no touchpad issues whatsoever. Then, I started experiencing problems once I began playing Ghost of Tsushima (PS5 edition), and the guiding wind function—a swipe-up gesture on the touchpad—wasn't working consistently, and then wasn't working at all. I took the whole controller apart, couldn't see anything obviously wrong with it, and put it back together. The problem was still there.
Later, in Spider-Man: Miles Morales, the issue was inconsistent, but the swipe-left function, to access the in-game crime reporting app, would still work most of the time.
Finally, I'm currently playing Hogwarts: Legacy, which doesn't seem to have any need for touchpad gestures, but when I tried to use the touchpad to type in some account information, it was wigging out, detecting gesture input that I wasn't giving it. Has anyone else run into this problem, and is there a way to fix the issue without buying another controller just to harvest the touchpad?