Strangeness when referencing VLs in other VLs

I have a virtual_libraries() column. However, I'm having a bit of a strange interaction with it and I'm not sure if it's a glitch or some sort of strange user error.

I have two VLs here:

Fiction: tags:"=.Fiction"

Cleanup: search:"=Cleanup"

I wanted to hide all the "Cleanup" books in the Fiction VL. So I did this:

tags:"=.Fiction" AND NOT #vls:"=Cleanup"

This search worked as expected when I tested it in All Books. But when I put it into the Fiction VL itself, it results in every VL disappearing from books that have a tag starting with Fiction.

Here's one book before and after modifying the VL:

Attachment 191275

Attachment 191276

The weird part is that all the VLs are still returning their correct books, and if I use template tester to run virtual_libraries() directly on those books, it still shows the correct ones:

Attachment 191277





I did some further testing too. Two VLs here:

Physical Books: formats:paperbook

Loans: formats:overdrive


No overlapping books between the two of them. But when I changed VL to formats:paperbook AND NOT #vls:"=Loans" I got the same results: VLs disappearing from books with a paperbook format, virtual_libraries() giving expected results.

Any clue what might be happening here?

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