@Lindr_ZA 

Hi, 
You can update the Deco E4's firmware to the latest version via the Deco app or web UI and check if it helps.
How to Update TP-Link Deco Firmware
 

If not, please confirm the following information.
  1. Except for Deco E4, are there other Deco models in your network? Please describe your network diagram in detail.
  2. Please check what Wi-Fi networks you have enabled on the Deco, such as the main, IoT, or Guest network Wi-Fi. Do they have the same SSID and wireless security type?
  3. For example, if your MacBook Pro connects to the Deco's main Wi-Fi network, please try changing the Wi-Fi name to a new one you have never used before, set the wireless security type to WPA2/WPA3 or WPA2-PSK, connect your MacBook to the new SSID, and check if the same "WPA weak security" message appears.

Best Regards