Oh! Also there was an additional issue where during a longer session where I was switching across multiple gamepads, the stick input got bugged such that it acted as if the directions were being briefly/rapidly tapped.
https://www.twitch.tv/annmwhite/clip/TemperedPolishedTroutFeelsBadMan-JE_2pxr0v9...
(Not visible via the built in input display, but I'm holding the stick tilted.)
I think this is a Godot bug rather than an X-YZE bug because I've encountered the same behavior in Brotato, and likewise the only solution I have for it there is to close and relaunch the game.