Chromecast Audio iOS media player

Following advice I got here on Audiogon I have a setup with a Seagate NAS Drive connected to my Wifi Router casting to a Chromecast Audio via toslink to a Yamaha S501 Amp. I had an iPad unused around the house and hoped to use it to control the music but I have had poor success in finding an iOS App that will play the files I created in 24 bit. The 16 bit stuff is fine on almost everything, but 24 gives all of them problems.The problem is the same in every app- intermittent "skip" on the bigger tunes. I think I’ve tried everything on the Apple Store that had a trial or free version and I have no problem buying something if it would cure the problem. Also Seagate's Media Player doesn't show any FLAC files on my system). At this point the better performers have been LocalCast, 8Player and MusicStreamer but each of them still has some issue with the "skip". I was going to try PLEX but it seems like I would have to load PLEX onto my NAS Drive before it could work with their music player. Am I destined to end up buying an Android pad to correct it or is there something in the iOS world that might solve my problem? I presume this isn’t DAC related because I presume using optical bypasses the Chromecast DAC and the Yamaha DAC is used instead?