It seems to appear every few Play tests I do when I start. I assume its not actually a studio bug but rather a website bug, it only appears in studio however.
I want to add to this, but I’m not sure if this would be the right way to do it. This also happens on the website and will stall the page load event until it returns a 503.
They should be in appdata/local/roblox/logs. It looks like you found them though. Send me the ones from the last session you had in Studio then, and I’ll see if there’s anything useful in them.