@Yuu 

What do you mean that some phones cannot connect well with the WIFI connection? Any specific symptom? Like the speed is slow or it is unstable? 

What is the led status of the router when it happenes？

At that time, please login to the web UI and take a full screenshot of the status page. 

Besides, who is your ISP and what is the bandwidth you paid?

When and where did you buy this router?

Good day. 

Cannot connect well means some phones will have unstable connection. Playing online game will experience lost connection from server eventually.

There's nothing wrong with theLED notifications. Everything works fine. And other devices works fine too with this router.

My ISP is Malaysia Telecom. 4mbps package. 

It is because some phone are not compatible with this router is it?

Both of my phones still experience this even I'm the only one connect with the wifi

I bought this modem from Telecom Malaysia December 2018.

How to solve this?

@Yuu 

Thanks for your clarification.

As you know, it is a heavy traffic activity to play online games, and considering the bandwidth is 4Mbps package, I suspect that it limits the performance.

You can try to enable/activate UPnP under access management-UPnP page to give it a go.

May it help and have a good day. 

@Kevin_Z 

Unfortunately, this issue still happening even I'm the only one using the internet