What causes download speeds to drop to zero after a few minutes when using an external WiFi adapter?

 
I have a high-speed internet connection that I access through an external WiFi adapter, as I do not have an ethernet option. When I start downloading files, I get an average speed of around 180 Mbps for the first two minutes, but then it suddenly falls to 0 bps and the download stops.

 
I am not sure what is causing this problem, as my internet works fine for other purposes.

 
I would be grateful for any advice on how to solve this issue.
 
https://technsight.com/