EDIT: I tried MC30 and I'm not seeing the same issues. Sorting seems to stay put and works as expected. Guess I'm forced to upgrade...
I only use MC27 to manage my music library of FLAC songs. Nothing else (no video, streaming, etc). I have it set to "Standard View" and no Grouping. So it looks like iTunes used to about a decade ago, just a "spreadsheet" view with Artist, Album, Track Name, Track Number, Duration, and Disc Number. No artwork.
1) I set up a custom sort titled "AADT" that arranges by disc, track #, album, and artist (that is, it displays the artist first, then the album, then lists the tracks in order, and lists disc 1 first, then disc 2 etc if applicable).
However, the majority of the time that I select this Sort, by right-clicking in the columns, choosing Sorting and selecting my custom "AADT" it does nothing, even when my library is clearly not sorted. Even if I choose a different sort, and then go back to AADT, it does change the sort, but not to what is specified as AADT (e.g. the tracks are not in order). I cannot figure out how to reproduce this. Sometimes it works, other times it doesn't. I have tried deleting and recreating this sort, but I still eventually have the same problem.
2) Sorting doesn't stick. I'll sort my library, then do some other operations -- maybe edited some Tags, maybe switched to a different tab, whatever... and I come back later, and my library isn't sorted how I left it. In my mind, sort should not change unless I explicitly click on the column headers (either left click to manually change it, or right click to select a saved sort).
3) When I plug in my iPod, and have it in the left nav area under "Drives & Devices", and drag some songs from my library onto it (keeping my library as the active focus and using the left nav as a proxy for the iPod), sometimes this drag operation will cause the sort in my main library (where I'm dragging from) to change. Other times it doesn't change. Again, seemingly random. It doesn't lose my place in the library, but what will happen is e.g. instead of the tracks of an album being in order the track order gets scrambled.
EDIT 4) I've also tried clicking the down-pointing triangle in the tab, and choosing "Sort By". This also doesn't work reliably. I'll choose many different sorting options, most of which are built-in, and the sorting of my library doesn't change. Even if I select something totally off the wall like "File Size".
Usually I can temporarily "fix" these problems by manually clicking on a column header, e.g. Album, and forcing it to sort by that metric, then doing one of the steps I mentioned above to get it to go back to my saved AADT sort.
Sometimes the tab label (in my case, "E:") shows in red font. What's that all about?
Thanks for the help!
Armand