Under Wayland, if a user has a panel on the top of the screen, the top of Yakuake is obscured by the panel. It appears that Yakuake lines up with the top of the screen, rather than the bottom of the panel. This obscures the top 2.5 lines of text (at least on my system), which can be problematic in some cases, so I listed this as 'major', but feel free to drop the severity if you figure it's not that much of a problem.
*** This bug has been marked as a duplicate of bug 378872 ***