I have two Raspberry Pi devices running the latest version of Volumio. One uses HiFi Berry and the other Schiit Modi. I have tried with both iTunes and MusicBee running the RemoteSpeaker plugin for Airplay.
No matter what music player I use, one device seems to be about a full second ahead of the other. I’m not even sure where to begin. Any suggestions? I have tried resetting then and syncing their clocks to a local NTP server.