iTunes library? Presumably you indexed the actual files on the network share into the Sonos library. They should be in the correct order if you locate the specific album in the index. If, however, you select the artist and choose ‘All’ then the tracks will be in alphabetical order.  

My music library is stored on a Mac.  I use the Music App (formerly iTunes) on the Mac.  When I open Sonos App and check on one of my albums, the play order for that album is not correct.  All of the songs have the correct number for the disks and for play order.  They are not in alphabetical order just out of order.  for example number 0ne song is in third place. Number 15 song is in fourth place.

If you select the album via the Artists view then drill down to the album, or via the Albums view, and the tracks are out of order then the metadata (tags) could be missing the required track number field. 

That is what is so confusing.  metadata is all there and correct.  iTunes displays it perfectly.  Sonos app shows the correct number for the track but tracks are not in numerical order, some are and some are not.

Do you have the ‘Sort Folders By’ set to ‘song number’ in the Sonos App Library Settings? See attached.

The track number metadata tags for the albums in my library here are shown as 01, 02, 03, 04 etc. and that format is working okay, if that perhaps assists you further?

Thanks for your replies.  This is happening on two of my 3,200 albums.  

If all other albums are fine I’d strongly suspect the metadata on those two.