@Wawan29 

Hi, 
You can refer to the instructions below to troubleshoot and check if it helps.
Fix unstable connection when connected to the Deco network
 

Please provide the following information if the same phenomenon persists.
  1. How many Deco nodes do you have? Please describe your network diagram.
  2. When the client devices connected to the 5 GHz have a connection issue, do they connect to the 5 GHz Wi-Fi but have no internet connection? What's the LED status on your Deco units?
  3. Do you have the connection issue on all 5 GHz Wi-Fi devices simultaneously, or only some of them have the connection issue simultaneously? Do the 2.4 GHz Wi-Fi devices have the same issue?
  4. How often does the connection issue occur?

Best regards.