I have the same issue:
CORE: MacBook with Mojave 10.14.6 (Early 2015); 16GB RAM; SSD (I should add that when listening to music the computer is only dedicated to Roon with lid and idle Sleep preventer, and even when I use DSP the processing speed is almost always from 80x to 90x)
NETWORK: Netgear NightHawk X10 R9000 router, NAS with gigabyte ethernet, Roon Core MacBook through WiFi 802.11ac 1,300 Mbps transfer rate, Fast fibre broadband (100Mbs measured).
AUDIO: KEF LS50w connected through ethernet to the router (this is where I had the issue); two airport expresses gen 2 with 802.11n 5ghz connection.
LIBRARY: Tidal; ~2,500 albums ~16,500 tracks in a NAS connected through gigabyte ethernet directly to the router.