I see this is a long-standing issue. I’ve just rediscovered it.
I had a folder at the root called “Bulk”, in which I put news feeds that are too high-volume to read everyitem. So sometimes I just mark the whole thing as read.
I wanted to split it up and have a News/Bulk and an Opinion/Bulk folder. I created two new sub-folders, and tried to move the items.
Well some of them worked, and some of them didn’t. And a few of the feeds got deleted. I re-added the deleted feeds, and selected the News/Bulk folder. They appeared in the Opinion/Bulk folder, and I cannot move them from there.