I am also experiencing this issue with Roon. Here is my set up:
QNAP TVS-EC1080 -> Cisco SG200-08 (Link Aggregation Enabled) -> Cat7 Cable -> Cisco SG200-08 (Link Aggregation Disabled) -> Cat7 Cable -> Lumin A1
Roon is installed on an external SSD drive connected directly to QNAP
Files play as expected when using the Lumin app, just no luck with Roon unless I use AirPlay.
Lumin updated to 8.01 Version
I’ve read through many other posts about jumbo frames and the QNAP does not have an option to enable/disable, just 4 values to choose from. I’ve tried each one and still no difference.
Also, can’t find any option to disable jumbo frames on the Ciscos.
I tested files locally on the Lumin using Roon and made no difference either.
Any suggestions would be helpful. Thanks