@David-TP 

Thank you for the prompt reply.

1. Fast Roaming" and "Beamforming has been disabled.
2. Mesh Technology has been disabled on the devices.
3. Only Devices on the Deco WiFi are experiencing issues (tested iPhone and iPads and the latest iOS). Tested on my old BT Disc and routers WiFi and experienced no issues.

I have tested with the suggested settings and I am still experiencing the issue however I have found that if I disable the WiFi and reconnect to the WiFi it works until i connect to another unit. I hope this helps!

It is rather frustrating having spent a lot of money on this mesh solution and the very basic operation is not working.

Kind Regards,

Suhel

  @suhel_a I was reading your post and this is just a shot in the dark but could it be possible that the X50s are exceeding the power capacity of the POE switch?  According to the X50 description, they feature 802.3at and comes wtih a 12v 1.5A power supply in the box (18w).  Regarding the POE capacity of the switch, according to TP-Link, the maximum output of each port on the TL-SG1005P is 15W with a total output of 56 watts.  According to the specifications of the TL-SG1005P, "when total power consumption excels 56W, the intelligent power management will cut the lower priority port power off to ensure the high priority port’s power supply and protect the device from power overload operation."  Is it possible that the. POE switch is cutting power to one or more of the X50 POE devices to protect against overload at seemingly random times?  

Deco X50-PoE | AX3000 Whole Home Mesh WiFi 6 System with PoE | TP-Link