Though I recognize that the D-pad is more sensitive to diagonal inputs than most controllers, I rarely get wrong inputs with my Pro's D-Pad, and when I do, I recognize that I pressed slightly to some other direction as well, so it is usually in fact my fault. In other words, I have the D-pad pressing almost down to a science. However, while playing Puyo Puyo Tetris just now, I got a severe sensitivity issue when pressing right on the D-pad: the console would always read D-right as D-up/right, unless I pressed right on the lower half of the pad, which is very hard to do without also activating D-down.
The problem persisted in the game and console menus. I reconnected my controller to the Switch, the issue was still there. I already gave up and thought the pad was busted and that I should send the controller back to where I got it, or to Nintendo. However, in my frustration, somehow quickly mashing D-pad in random directions for a while managed to fix it. At least for now.
Just thought that was kinda strange. Maybe there was some dust stuck underneath the D-pad that interfered with the inputs, and mashing the pad made the dust go loose and come out from under there? I dunno, but I am a bit worried the problem will reoccur, possibly even worse than it was this time. Glad I got it working again, though.