Roon RAAT and "An audio file is loading slowly"

[ogs]

I use two HP ProCurve J9085A switches (6 meters apart) linked with Gig copper and vlan trunking between them. My router is a Palo Alto PA-220 firewall (with a Cisco DOCSIS cable modem in front), but nothing is directly connected to the firewall other than the "inside" interface. All layer two is handled by the two switches and a Dlink 505 wireless unit in bridge mode for the Android remotes.

The two switches have each 24 100BASE-T ports, two 1000BASE-T and two SFP slots (that are not used at the moment). The switches are completely silent and fan-less. Roon Core is connected to one switch while the Devialet amp to the other, both on 100Mbps ports. So there is a gigabit link between the switches, but what matters seems to be the ports devices are connected to. Ethernet cables are cheap Cat5 with no shielding.