If it helps, I identified another site that renders weirdly like this. It's always the same sites consistently, but I cannot identify what their common denominator is.
Looks the same on Opera and Opera GX (with a blank profile and all blockers disabled)
https://spielzeugblog.net/ratgeber/lego-alternativen/
6cf27ba5-a6f5-4c1e-ba89-604e8f953b1e-image.png