@Martin010 my 5 port smart switch started doing this and I found this post.

After some troubleshooting, moving of cables and playing with settings I discovered the issue. It has absolutely nothing to do with Sonos as I don't own one.

The blinking orange and green LEDS indicate that A) you have loop detection turned on and B) you have a loop (two different paths to the same device which is not allowed on a local network). 

Reconfigure your network to remove the loop or turn off loop detection. 

Hi @xjonx, Thanks for the info. It would match my posts, as I mentioned some Sonos devices are both wired and wifi connected, and apparently during an update this caused the issue. I have not seen it anymore since.. It would be nice however if TP-Link would include this in their manual, would have made troubleshooting a lot easier.

@Martin010 

I had the same problem with my TP-Link M9 Pluses (3 nodes) set up with Ethernet cat6 back haul.  My TL-SG116E v1.28 switch showed the same behavior.   In my situation, one of my M9 nodes connected both by Ethernet and the 2nd 5Ghz WiFi signal.  Only one node exhibited this behavior.   I noticed the status in the tp-link cloud app did not display Ethernet in the tp-link cloud app, it showed 2.4/5_1/5_2Ghz which should be incorrect.   I used the Network Optimization feature in the app and that seemed to kick the M9 node off of Wifi back haul and into Ethernet back haul.  Now my TP-SG116E ports show only green lights.