That is not entirely true. I have been experiencing the same error. I've got 8 pending items in the work queue and a lot many more like completed items, so I know that the stage as Get Next Item works and it has worked in the past, but now, it doesn't correctly with these new elements.
I've tried repeated times to delete and load again the items but it doesn't work.
I've also tried to see if BP recognizes these elements and some of them don't, so I think that's the problem, but I don't know how to solve it.
Which could it be the problem of recognition of these elements in the queue?