@PrimeBrett 

You have replaced single WiFi router with WiFi mesh. What you have found is old devices may not understand WiFi mesh or don't know how to handle it. This is especially common with Smart TVs, security cameras and IoT devices. 

It is not TP-Link Deco specific problem. It is the problem of switching from single WiFi router to WiFi mesh. When I say "old" devices I don't necessarily mean something bought in 2010. You could buy something brand new today, but, for example, if it does not support WiFi 5GHz and only runs on WiFi 2.4GHz - that could mean its WiFi code has not been updated in ages. It could have been written when WiFi mesh was not yet a common thing for a regular household. 

So, the bad news: if you switch from TP-Link to a different WiFi mesh brand, you may see same or similar problems. Different WiFi mesh systems run on similar technology and same WiFi mesh standards. 

You can go back to single router setup you had, perhaps with more powerful router for better coverage. Also, you could consider older technology: WiFi Router + WiFi Range Extender combo. 

WiFi mesh really shines when you stream something on a smartphone while walking around the house. For stationary devices, such as security cameras and TV, old school WiFi Range Extender without mesh functionality is enough.

Having said that, there are few things you could still try with X68, which might help. Here they are:

1. Assuming you have everything connected to Deco Main Network, in Deco app turn off 5GHz for Main Network and leave 2.4GHz only. If there is a separate option for WiFi6, turn that off, too. Leave just 2.4GHz.

2. For each stationary device such as security camera and TV, in Deco app turn off "Mesh" toggle for it.

3. If possible, bring Satellite X68 to where your Samsung TV is, and connect them by Ethernet cable. Most Smart TVs have Ethernet port. Out of my personal experience, until I wired my Sony TV to Deco node by Ethernet cable, I was always unhappy with quality of streaming.

4. I checked hardware specs for Nvidia Shield TV, it has Ethernet port. Try previous suggestion, but with Nvidia Shield TV.