@bazaria 

Hi

You could refer to the following suggestions:
1.You could disable QoS from the Deco APP, you might not see an on/off switch for QoS, in that case, please set it back to standard and remove all priority devices.
2. Disable SIP ALG and UPNP from the Deco APP >> MORE >>> Advanced menu.
3. It is recommended that you create a guest network for one of the devices. Open the Deco APP, go to MORE > Guest Network, enable the guest network feature.

If the above suggestions do not resolve the issue, please provide the following information:
1. How many client devices do you have in your home?
2. When did you purchase Deco and when did the problem occur?
3. When a problem occurs, it is recommended that you restart Deco to verify whether the problem will be temporarily solved.
Good day.