DnD surfaces often currupted on the first frame(s?) on Wayland
When using DnD with Wayland clients I regularly see them being corrupted on in the beginning, both when starting DnD and when dropping on an invalid area, starting the "fly back" animation. I'm not sure if this is a Mutter or GTK3 issue though (so far I've mostly seen that in Nautilus and Firefox).
They usually show garbage content as if the buffer was commited with uninitialized data, often showing content from different surfaces (at least it looks like that).