2024 Goldwing DCT stalling and no riding mode shows, DCT initialisation failing

My modern DCT Goldwing is stalling while I am slowing down. It is not happening at a complete stop—it cuts out while decelerating from 50 mph down to around 30 mph.
We checked the battery terminals and they were a bit loose, so we tightened them up, but it didn't solve any problem. The engine still shuts down on deceleration. On top of that, the dash isn't showing which riding mode I am in anymore and it won't let me switch between manual and DCT.
I tried doing the standard DCT clutch initialization procedure to see if that would fix the stalling. I could hear the clicking from the DCT and the bar would flash every 2 seconds, but then it just started flashing rapidly and failed. During the initialization attempt, I could also hear a sound like small metal pieces jumping around inside.
Now I also have an amber Hill Start Control error light on the dash (H with an exclamation mark). I checked all the fuses, including the 5A ABS ECU fuse, and everything is completely fine.
I am giving up on it for tonight and riding it as is back home to New Jersey tomorrow morning since it still starts and gets into Drive. If anyone has experienced this exact combination of problems—stalling while slowing down at speed, lost ride modes, a failed initialization with a rattling sound, and the H! light—let me know what the actual issue turned out to be.