@exactspace 

Your deco s4's may have different hardware versions between them.

Some versions of it don't have 1.6.1 listed.

https://www.tp-link.com/us/support/download/deco-s4/v3.6/#Firmware

  @MDA400 

I see, that doesn't sound good at all. I suspect this is why I am having problems. 
 

Seems misleading that TP-Link would name these the same thing, even though they have different hardware, and possibly the inability to update. 
 

I've looked this problem up online, and I'm led to forum posts complaining about the same thing. 
 

Any way I can return these to tp-link to get the updated ones?

  @exactspace 

I would ask tp-link support if anything can be swapped,  but if you are past a return window when you bought the units they would not necessarily be obligated to do so.

https://www.tp-link.com/about-us/contact/

  @MDA400 

Thanks I'll contact them. I think they're obligated if they are false advertising two different devices with the same name that cause problems together. Plenty of people complained about it. 

  @exactspace 

Hopefully they can fix it with a firmware update so that you don't need to return or purchase anything.

  @exactspace I suggest swapping two Deco satelites, to understand if the issue follows the Deco unit.