I have had similar issues during the last few days.
I have uploaded several albums using Google Chrome in Incognito mode. All tracks are visible in the web interface after the uploads are completed and the browser window is refreshed.
However, some tracks are missing from several albums both in the VOX Player for Mac and in the iOS App. The tracks are not visible in artist view, album view or track view.
I can see and play the missing tracks if I do a search in the iOS player app. However, the tracks are not associated with an album, which seems to be the reason for them not appearing in artist view, album view or track view. Therefore, I’m not able to delete the tracks in VOX Player, since the tracks are not associated with an album.
I upload my music in FLAC format lever 5 using MediaHuman Converter, so the files are newly tagged and not messed up with any third party tagging software. I have used the same setup for months wit no problems.