Edit: This has now been fixed, all projects now show the correct thumbnail.
Or maybe it's just my internet being changed…

Old info:
My browser / operating system: MacOS Macintosh X 10.15.7, Chrome 93.0.4577.82, No Flash versions detected

If I'm either accessing my stuff or posting a project to a studio, scrolling down towards my past projects shows that they got defaulted to the Scratch 2.0 default project thumbnail.

Here's proof:
“My Stuff”

“Adding Project To Studio”


Please resolve this soon, certain resolutions are bugged because of the cdn servers.