Search within search results: problem in 6.0.3 and also in latest v5

[BarclayB 2]

In v6.0.3, I have a saved search that does: notebook:N1 -tag:Hidden which works to show all notes in N1 that do not have the tag "Hidden". When I then click in the Search Notes box, all of the notes disappear and it says "no matching notes found". It should of course keep displaying all of the same non-hidden N1 notes until I start typing a search term. Worse, when I type a search term, it finds nothing in the N1 notebook, thought it helpfully suggests OTHER notebooks where this search term appears. 

In the latest build of V5, something similar happens. I use the shortcut and see my N1 non-hidden notes as above. When I click in the search box, the notes are still displayed as they should be, but when I type a search term, nothing is found. 

This behavior does not happen when i start by clicking on the N1 notebook, displaying ALL notes in the notebook, and then type a search term. All works fine. 

With further testing, this seems to ONLY happen when the saved search includes a "notebook:xxx" term. If I use a "stack:yyy" then the problem does not occur. This is a workaround--create a stack with only that one notebook and it all works fine! 

The problem seems to be when trying to search WITHIN search results and and it seems to have happened with a recent update to v5, and now is carried into v6. This has all worked fine for years until very recently. 

BB