Audiobook tracks not being selected by playlist mixer

[Pingaware]

Windows 10, v3.4.8001 P.

If you select "audio books" from the drop down "Library" menu under music track source when creating or modifying a Playlist Mixer criteria, then try to select by album within that same criteria (i.e. Album is a specific value), matching files from the audiobook section of the library will never be selected by the mixer.

Noticed this in an existing playlist mixer, but I can reproduce it in a brand new one too - however not with every album. To reproduce:

1. Create a new playlist mixer
2. Add track selection criteria
3. From 'music track source', ensure 'audio books' is ticked. Music library does not need to be unticked
4. Set a rule of "Album is [an album that is in the audiobook section]"
5. Nothing shows up when mixer refreshes after saving rules

I haven't played about too much to find out what's not working, but it seems like it is only ever pulling tracks from one specific album in audiobooks. If a rule is set such that that album can be chosen from it will display that, otherwise nothing else is ever selected. The specific album it's drawing from doesn't differ to others it should pull from in any meaningful way other than it's the one with the earliest date added value.

I had a quick check and auto-playlists worked exactly as I expected (i.e. all rules are being correctly followed).

[Steven]

By default audiobooks are excluded when shuffling is enabled. If you do have shuffling enabled and want the audiobook included, edit the Settings tab in the Tag Editor and untick 'exclude from playback'

[Pingaware]

Damn it, thought I'd checked every setting that would be relevant.

However I thought that would have explained it, but Album A (the only album that is being selected by the rules and the one with the earliest date added value) has the 'exclude from playback' flag ticked too, yet it's still appearing. So I think there's something a little weirder going on.