Moto G5 Plus Wi-Fi disconnects every now and then Moto G5 Plus (XT1686 - Boot-loader locked) running on Stock Android 8.1.0 with latest security patch(August 2018) disconnects from Wi-Fi network for no apparent reason. My device is right next to the Wi-Fi Router (Other devices have no issue with connection at the same location) , the Network strength is high. 10 seconds after getting disconnected from the network, it tries to connect back to the network and it works for another 2 minutes before getting disconnected from the network. 

This issue occurs randomly (Could not blame/pinpoint certain installed Apps). I booted into Safe mode to check if it happens because of a particular App on my phone. But the issue occurred on Safe mode.Also, I don't think the problem is my Wi-Fi Router(D-Link DIR-600M) because the issue occurs with WiFi Routers at my workplace, Friend's home as well.  

I tried every workaround mentioned in the forum here.


I have turned OFF Turn off WiFi Scanning
Forget Network, Add it back manually
Tunnel the network through VPN
I have factory reset several times hoping to fix the issue but to vain.
I have reset the Wi-Fi network, changed Router configuration from Auto Channel to a fixed Channel
I have changed the Router configuration - Security encryption method to WPA2-PSK, WPA-PSK


I have no clue as to what is the issue here, I'll be grateful for any Fix / workarounds / Creative solutions. Let me know if you need any more information.
Actually, the issue here seems fairly clear in looking at your troubleshooting... discounting the fact that your router is 9 years old and likely not up to current standards, you did state:


  I don't think the problem is my Wi-Fi Router(D-Link DIR-600M) because
  the issue occurs with WiFi Routers at my workplace, Friend's home as
  well.


Considering you have tried this on multiple networks and connections, and you have factory reset and performed a network reset multiple times, the conclusion can only be that your phone is defective. You should contact Moto for a warranty replacement, or just consider replacing it if it is no longer under warranty. 

In looking at all the troubleshooting you have done, and given the above quoted statement you made there doesn't seem to be any other possible cause.

There is no known issue with WiFi on the Moto G5+ in any Android version or release, and since this is not related to a single router or connection, the issue seems quite clear, your Moto is defective.