I see the same thing when I try it. But if I click on Collection D and then click on Collection C, I see the photos in Collection C.
Thanks for verifying what I saw.
Unfortunately it becomes murkier and murkier. I notice that I had both a folder and a collection highlighted on the left hand side of the screen. Selecting another folder did not clear the collection highlight. I would test further but then I closed LR and reopened and now when I select a folder the collection "un-highlights" and vice versa which makes sense to me: either you are looking at a collection or you are looking at a folder.
And now when I go to the keyword list panel and select a keyword that points to a photo that is not in what is highlighted on the left, the photo is displayed and the highlighting disappears from the left hand panel (collection or folder). Again this makes sense: either you are looking at a folder or a collection or a keyword set of photos.
So all I can say is that it is working now (for me) and if this pops up again I will close LR and reopen it. This UI is complicated and the bugs equally so
I notice that I had both a folder and a collection highlighted on the left hand side of the screen. Selecting another folder did not clear the collection highlight.
This bug has been outstanding since at least LR 5.7. Please add your vote and details to this bug report in the official Adobe feedback forum: Lightroom : Selected Published Folder or Collection is not deselected if a folder is selected | Photoshop Family Custome…