I can confirm that after a day of being plugged in directly to the cable modem that 1000M is maintained without degradation or issue. Is there a setting on the ER605 that I should further look into?

Hm bummer, I've replaced cords and couplers and the problem still persists. The uplink reports 1000M on plugin and after a while it degrades to 100M. I can also verify that plugging this same coupled...

Dang you might be right after all @dsj ... still drops even after latest firmware and reboot. I have a 50ft wire between the two wires plus a 4ft + coupler between the two. Just switched out the wire...

Nevermind! Found it under Status -> Traffic Statistics -> IP Statistics up top. We'll see how this does. Thank you!

Thank you for the reply @dsj. I am not so sure on the cable, but one thing I noticed is that the router it went to (also a TPLink router) had an older firmware version. So I applied that and we'll...

Alright so after some digging it appears that the port in question has its speed go from `1000M` to `100M`. No reboot is necessary. Simply disconnecting it and reconnecting it resets it to 1000M....