I have a similar problem that started with 1.3 and continues. Every time I add an album to the Watched Folder only the first track or two will display.
My work around is to have two folders in my Music Folder (designated as the Watched Folder). I add the album to the first folder (and Roon only shows first track or two). I then transfer it to the second folder (where all my albums reside). As soon as I do this Roon picks up all the tracks.
The folks at Roon (and Salk Sound, the maker of my streamer) have been unable to duplicate this behavior, so have been unable to identify and fix the problem. 
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Fortunately my work around is simple and quick, but annoying nonetheless.