I will put a video here in a few moments because it took me almost 6 months to just come of with the idea that it might be this yesterday when my friend stood on it and my other friend and I held the wheels in place and watched as he tilted back and forth.
The two bits a the end turn sideways. Very odd haha and yes I totally get the falling off thing! You tilt, and then the board doesn’t turn, so you tilt further and just lose balance
Here ya go. It is kind of hard to see in the video but in person you really can tell that the deck flexes a lot in that space. As decks go, it is quite thin as well and that does not help it in that regard.