Hello, some minutes ago I was on scratch and looking at some projects, then this happenend:

I think its some kind of webgl mesh detecting bug.
Also it have happenend other times on other projects and it keeps appearing.

Other info:

I had only scratch and the windows alarm program open.
In case you wanted the project here it is: https://llk.github.io/scratch-gui/develop/#531017159

My browser / operating system: Windows NT 10.0, Firefox 87.0, No Flash version detected

/starkodder