@Bluebeep 

Do you have Site to site VPN or L2TP/PPTP configured on your router?

Hmm, im not seeing this at all on my network, which is probably more complicated than yours too

I have an ER605v2 as my primary gateway, which tunnels VPN connections to an ER7206.

I have an RDP client on a vlan off my ER7206, and can both RDP into that machine over the vpn without any issues (so far i had one user logged in for 2 whole days because he forgot to log off lol) and can also RDP to the machine from the ER605 vlan without any issues

  @GRL 

Ok the reason I asked about VPN is from previous experience.
I have a lot of VPN on TP-Link and have VPN to many TP-Link sites and Site with Cisco firewalls, both with S2S, L2TP and OpenVPN, what I have had problems with is that the network drops when the VPN connects or reconnects. I got a beta from TP-Link on all router models that solved this on S2S and L2TP, it's still not fixed on PPTP, 

ER605v2 still has this problem on S2S, L2TP and PPTP with the official firmware, it has not been updated for a long time.

You should compare the event log and see if there is any connection between VPN connect and RDP drop on your LAN.

  @Bluebeep 

Are you still able to Ping the remote desktop PC when the issue happens?

Is there switch/other network devices between your PCs and the router?

You mentioned you have tried static IP on the PCs, have you tried to remove the router, only leave the PCs and the switch connected, and test remote desktop application(via static IP)?

  @shberge 

I do have VPN configured but it's only OpenVPN. (Client-to-Site, not Site-to-Site). This is for a couple of remote workers accesing the network from home to RDP into their systems.

I looked in the router and the system logs default configuration shows me basic information and I'm not sure if modifying the severity will show me when users will connect to the VPN. So I have asked users to keep a log of each time they connect over to the VPN and asked LAN users to keep a track of when RDP disconnects and hopefully there is a match somewhere.

I have attempted to connect to the VPN myself but haven't found an issue with RDP at that exact time yet. Still collecting data on that through the day today to see if there something there.

I'll report my findings.

Thanks!

  @Somnus 

I haven't attempted to run a consistent ping when the disconnect happens. I'll test that on one system. Though as soon as the disconnect happens the users are able to reconnect immediately. I'll run a ping -t and ask the user to send me a screenshot of the command window the moment the disconnect happens to see if there are any drops.

The network is quite straightforward. All computers are connected to a switch which is in turn connected to the router. My switch is a TP-Link TL-SG1016PE and I did reboot it last night. I also checked for firmware updates yesterday and there have been none released for my hardware version (v2.0).

I haven't tried removing the router from the mix entirely coz the disconnects happen randomly. Sometimes it 2 hours before users get disconnected. Though it's a good idea, it's very difficult for me to suggest that because it's in a production environment and folks can't be without internet for even a minute nowadays. So suggesting to wait for RDP to disconnect for a couple of hours would probably get me fired lol

Just kidding.. But you see what I mean :)

I'll report back my findings with the ping output when the disconnect happens.

Thanks!

  @GRL Honestly this is my first experience with TP-Link routers. We were a Cisco shop for about 15 years and lately they dropped their SMB line I believe and haven't gotten back to us about when/if there is new product. So we had to jump ship to something else that works.

I'm super impressed with the options available in the TP-Link router. Spent like an hour just browsing through the menu system lol

Maybe it's just a learning curve with the new equipment or maybe I got a lemon. But glad to hear your setup works so I don't lose faith in the product.

Just a thought....

If you have any of the TCP / UDP flood defenses enabled in the router, try increasing the packet rate detection settings on them 

  @GRL I honestly left everything at their default values. It seems like there is nothing configured for defense. I kind of make sure that I have one thing working before I activate another thing in case something screws up I kind of know where the issue might be lol

Here's what I have on the Attack Defense:

Are you port forwarding RDP to the server (TP LInk call this Virtual Servers for whatever reason) or have you set it as a DMZ ?

EDIT, scratch that, i see you have VPN instead so its being accessed as a local resource