triplicate panel objects in Plasma

Every app opened causes three Plasma panel objects. In the screenshot, only one instance of Konsole is open, and one instance of Spectacle:

I tried deleting the content of ~/.cache/ while logged out, but that changed nothing apparent. I would try same with whatever file in ~/.config/ controls panel config, if only I could figure out which that is, but no filename there contains string anel. plasmashellrc only contains the following:


[PlasmaViews][Panel 2][Horizontal1680]




Is this a known problem with a known solution? Searching for various combinations of panel and kde and/or apps and/or icons, etc. on and produced nothing related I was able to spot.

Found and solved by deleting plasma-org.kde.plasma.desktop-appletsrc. has the bad file, and the new file, and a diff of the two. I’m having no luck determining where the problem with the original lies. Can anyone else?