Hi SpaceDimSum! I use a PS4 Dualshock Controller on Windows 10, my CPU is an intel i7 with 16 gigs of RAM if you need my specs. My controller is plugged directly into my system, no bluetooth/wireless. Inputs are read properly elsewhere in the game. With X I am able to jump and ollie just fine. I've been trying the minigame off and on, it only somewhat works if I mash X and O alternating- sometimes I am able to get a hit or two out if I'm lucky. I haven't had issues with inputs on any of my other games; Not on Steam, Not on Dolphin, Not on any other game I've run.
If there is anything else I can do to help iron out this specific issue, I'll be happy to help! Thanks for your time