Turns out my game was somehow not installed correctly. Because it’s a legacy game there is no uninstall option (which is what I would’ve tried) but you can right click the game in the grid -> Show Game in Explorer and delete the file to force a reinstallation. After reinstalling, the size of its .swf tripled.

I guess the game was downloading during the white screen and I must have closed and interrupted it.

But thanks for checking, I wouldn’t have discovered the solution otherwise!