I'm not sure? What exactly does panel refer to in this context?

the're both part of plasma - panels and widgets

maybe there something corrupt in ~/.kde, could you try as a new user which you would have to create using systemsettings http://docs.oseems.com/general/operatin ... d-new-user

I created a new user, logged on as that user, switched to grid desktop, and the problem persists.

EDIT: the rotate and resize buttons now work on both users (they didn't previously) and they act like I'm in the default desktop mode, not the grid desktop that I have it set to.

EDIT EDIT: it appears that this was because the 'default' control bar was previously behind the 'grid' control bar, as now I can't access the buttons on the 'grid desktop'-style control bar.
EDIT EDIT EDIT: and now I find from further messing around that it only happens in the "air" desktop theme; switching to the other one supplied by default, "Oxygen," removes the problem. I'll take that as a solution, for now!

EDITx4: Never mind, Oxygen just has more opaque control bars so it was harder to notice.

I've never used the grid layout but I see now what your seeing though I don't know why the grid layout has it's own control widget bars (for me the overlay each other, not display to the side), at some points I can see both on diff sides of a widget.

For me this only appears on the grid layout not on the others I tested

You could post a bug on bigs.kde.org, you may need to create a new account iirc

If it wasn't for this problem I'd like the grid layout, since it appeals to my OCD. I'll send the bug report, soon as I figure out how. Thanks for your help!

found 2 existing bug reports, you should confirm (including your distro & KDE version) and vote on the 2nd
https://bugs.kde.org/show_bug.cgi?id=307720
https://bugs.kde.org/show_bug.cgi?id=277560