Has anyone had a problem of audio files perceptively glitching or buffering?
Files are all mp3s, and triggered with wireless MIDI from QLab through the IAC network MIDI bus on a Mac Pro.
The mac is connected directly to the wireless router (Apple Airport Extreme), which is less than ten feet from the iPhone 5s.

I haven’t had that issue - does it happen for any audio files? is it fairly consistent, or does it happen more randomly - if its consistent, can you send me an audio file that it happens consistently with?

assuming it’s inconsistent - the only thing I can think of (which really isn’t that helpful) is the device could just be screwed up - you could try reinstalling the os on the device (factory reset) and then try everything again…