Connection drops with USB Wifi adapter

Hi everyone,
since my laptop if far from my NetGear access point, I bought an external USB Wifi Adapter with antenna and it reaches very well my AP. Ookla Speedtest says the same speed as the wire connected devices.
The problem is when the download speed reaches its maximum rate (about 9 / 9.5 MB/s): the adapter stops downloading, ping to the router fails and the wifi icon on the tasktray turns into the world icon (no connection). I have to unplug the USB adapter and replug it or disconnect the wifi connection and reconnect it to have it working again.
If i take my laptop near the AP and use the internal Wifi connection, it doesn't happen, it never disconnects.
I made a try with another laptop and the problem is the same.
I think the problem is the wifi adapter, I already sent back it to Amazon and bought another one, with no luck.
The chipset of the USB adapter is Realtek 8812BU.
My Windows version is Windows 10 Pro 21H2 (build SO 19044.1415).

Do you have any suggestion?

Thanks

Samuria said:

First check the signal strenght if its 60 or elow it will drop second check the router channel is there any other network on the same channel with bigger signal? Third any electric between you and router like microwave, tv etc that can mess the signal?

I forgot to mention that the wifi network I'm connecting to is 5 GHz and it is on a channel with not other 5GHz wifi networks nearby.If I limit the download speed to 5 or 6 MB/s the connection never drops. That's the strange behavior.