It seems vastly higher on every region and VPN I've tested, so I think this is a case of the "technicalies".
It is technically 20%, because a bunch of the requests that happen on page load do succeed. Just not the few crucial ones that are required for the page to load correctly - those return a 500 the vast supermajority of the time.
Feel free to disregard this because ultimately its a tangent that doesn't matter; but supermajority is specifically a political term referring to the required threshold to advance legislation when simple majority isn't procedurally enough. It doesn't mean simply a greater share of.a majority
20% of requests on a GUI page also makes the whole thing unusable.
I can't get a single PR or issue to work. Maybe it's "20% globally, 100% anywhere people are awake".