May I suggest that you download and install a Wi-Fi analyser to show if there are any foreign Wi-Fi broadcasts interfering with your own Wi-Fi signals and where there are poor signal strengths..
From there you can look at refining your own Wi-Fi broadcasts.
I use this one ...
WiFi Analyzer Premium - Apps on Google Play

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BT Smart Hub 2 with 70Mbs Download,18Mbs Upload, 9.17ms Latency & 0.35ms Jitter.