Total wifi affecting connection on one computer

[HENDLD]

Hi, I am looking for some help please. 

I have total fibre and have never had any issues with signals. However my daughter has recently had a computer bought for her in her bedroom which is in an extension. The wifi signal in this room is very poor so I have upgraded to the total WiFi guarantee. I plugged the disc in the kitchen which says it is an excellent location and my daughter also now gets an excellent signal in her bedroom as does the rest of the house for which I have used the bt app signal checker in all rooms. 

My problem is that the WiFi signal on my sons computer shows 4 bars and an excellent connection but regularly drops to 2 bars and as he uses it for gaming it is becoming a real problem for him. No other devices in the house have a problem dropping and signals are always excellent, just my son who has a problem. His bedroom is right above the main router so i can't see why it would be dropping.  All i can think is that for some reason it starts to pick up the signal from the disc in the kitchen which is further away? I have started all devices and routers  again. 

Is there any way I can fix this?

Thank you very much. 

[Les-Gibson]

A couple of thoughts, the first of which is nothing to do with your problem but strongly recommended anyway.

have you turned off smart setup? https://www.bt.com/help/broadband/what-is-smart-setup-on-the-bt-hub--how-can-i-turn-it-on-and-off-

Have you thought about trying the disc in your sons bedroom? This should offer two advantages

1. Your son should have a good strong and consistent signal and
2. The disc should still have the range and ability to cover your daughters bedroom

[HENDLD]

Thank you les. I will try your suggestions and fingers crossed. 

Thanks again.