Chassis grounding the fmc to an Entreq grounding device along with any switches you have improves things further.
Network Acoustics Eno Streaming System vs SGC Optical Isolation System
Has anyone directly compared between the two? If my conversion isn't off, it looks like the Eno Streaming System is roughly $1,000 compared to the SGC Optical Isolation System at $350 (sale) w/linear power supply.
Eno:
https://www.networkacoustics.com/product-category/streaming-systems/
SGC Optical System: