@cjferoussis 

This feature, disabling Smart DHCP, will become available in firmware 1.6. That firmware may or may not be released for X20 V1. Can you share Update Deco screenshot from your Deco app, to see what else you have in your Deco mesh. You only need one Deco that supports this feature to run as Main Deco for feature to become available in Deco app.

Example of screenshot I am asking to share:

  @Alexandre.  Thank you for your reply! Here is a list of the Deco units we use (X20, M4R and S4). Have we got any information regarding the date of the update? 

Thanks again!

  @cjferoussis 

I am not from TP-Link, so I would not know, but even TP-Link Support that checks this forum is not privy to that info. 

I can see you have M4(R) hardware V2 and S4 hardware V2. You may be in luck, check this forum topic, under the table of the first post: Smart DHCP on/off option under Access Point mode

If you get beta firmware for M4(R) V2 or S4 V2 with that feature, you will need to promote updated M4/S4 to Main Deco: Changing the Main Unit for your Mesh Network

Another option would be to get Deco model that supports turning off Smart DHCP and add it to Deco mesh as new Main Deco. How to Set up a new Deco to be the Main Deco

I would recommend M5, they all regardless of hardware version have that feature.

You know that in Access Point mode you don't need to pass all traffic through Main Deco, right? You can just add new unit as Main Deco, connect it anywhere to your LAN and you are done. Of course, ideally, you should connect it to free Ethernet port of your router/gateway.

These options will not fix the underlying root cause. Deco Smart DHCP will be enabled if primary DHCP server in your LAN goes down. Usually, as soon as primary DHCP server is back, Smart DHCP will be turned off in Deco mesh.

The question would be, why would you lose primary DHCP server, which is not good. Another question would be, why does not it restart DHCP service after it is back. In some DHCP servers there is a configuration option "do not start DHCP service if another DHCP server is running." If yours has it, turn it off and problems with Smart DHCP should go away.

  @Alexandre. Thank you for all the information provided!!! I will try to set another deco as a main deco to see if I get the option to disable the smart DHCP server. Our network is quite big with multiple switches and for some reason, the main deco (that is not connected directly to the router that hosts the DHCP server) seems to lose connection with it. Maybe I will move the deco directly to the router to see if it solves the problems. I appreciate your time and effort! Thank you again!