Roon Server (current version) running on Mac Mini (Mac OS X 10.11.6 15G1004 64bit Intel i5) 8GB RAM, 1 TB disk, 3TB USB drive containing 94,000 FLAC files organised by Genre/Album Artist/Album/
Roon Client running on Win 10 (10.0.14931 64bit) 8GB RAM, 24 GB disk and iPad Air 2 running iOS (9.3.5)
I take only production releases for Windows 10 no fast track etc
Network: LAN Devolo 1200+ powerline Internet is fibre
No internal firewalls
Playback for main device is through SonicOrbiter SE and LH Geek USB DAC.
Secondary devices are Clint Digital Odin and Freya speakers.
You have the screen-shot of audio settings.
Is there anything else you would like to know?
The simple facts are that the problem presents on both an iOS client and Win 10 client with Airplay endpoints and wired Sonic Orbiter. It may be a server-side issue on the MAC.
Thank you for your kind assistance.