Hi guys, I’m having the exact same issue. First, it started when the Start and Coin buttons wouldn’t respond in any emualtors (And pressing Start would also hit SW8, randomly), and after avoiding using the start input and changing it to Switch 1A and remapping inputs via the ES config tool, now, pressing left on the joystick causes button one to fire as well as jump. Weirdly.

I also am very interested in hearing workarounds, or solutions. I’ll keep tinkering myself and try and post my results.