I played the web build. I'm on Linux, and my browser is Vivaldi (Chromium based). My gamepad was an 8BitDo Pro2 connected via USB in XInput mode. I have seen it occasionally have a disconnect issue, but not recently, and most games seem to be able to pick it back up after the short disconnect. It happened during the transition, so I don't know the exact point when it happened, and when I looked at the controller it was connected and recognized. I tried unplugging and plugging it back in, but it still did not detect. I just did a quick test on the title screen and it handled the unplug/replug just fine there, so I'd guess something during the transition itself.