I have two of the TP-Link TL-SG108S-M2 connected over CAT 6 Ethernet (approx 60-80 feet) and have various 100 Mbps, 1Gbps, and 2.5Gbps devices connected on both switches.  On one switch the 2.5Gbps devices are PC's and when "asleep" or off drop down to a 100Mbps rate.  It appears after some length of time the connection between the two switches drops down to 1Gbps and acts quite a bit slower.  I am on 2 Gig fiber and when I do a speed test with things as normal get about 500-900 Mbps down and upload speeds.  but when the link between the two switches has "dropped down" it slows down to 10's or less of Mbps.  And it wont auto negotiate back up, I have to unplug the port cable and replug it in.  it connects at 2.5 Gbps rates and run the speed test immediately again I will be back up at the speeds expected. When running slow I can run a speed test on my phone and get high through put over the WiFi.  

With this being a un-managed switch I would expect the switches to stay or auto negotiate up as traffic on the port goes up. 

I have moved the ports around but in the morning they have gotten back into the state of being a slow connection between the two. 

When other ports on the switch are at 2.5Gbps connections the switches stay connected at the 2.5Gbps rate but it seems like when nothing on the switch is at 2.5Gbps it dops the connection between the two down and never bumps it back up.

any thoughts?