This required End to end Testing required.
As you confirmed connected Switch if you connect Workstation it all working fine as per your mesages.
so you need to post us your topology. how these network connected.
You need to start from end connected switch to until server, where you see the issue. until we know HLD of your network at this stage hard to say where it was wrong.
Try to capture Wireshark from PC, each switch to see which point you can see lagging.