What can cause the speed of distributed wi-fi through a smartphone to drop?

Question

Computer networks

Phone Xiaomi Redmi Note 8t. Simka Megfon with unlimited Internet, without restrictions on its distribution. I measure the speed on both devices using Yandex.Internetometer.

Recently (a little over a week), when I'm at work during the day and distribute wi-fi using an access point in my phone to a laptop, strange things happen with the behavior of the network speed. After I connect to the distributed network, the speed on the laptop drops from the usual 20-30 Mbps to 200-500 Kbps in a couple of minutes. But as soon as I measure the network on the phone, which always fluctuates around 30-40 Mbps, the speed on the laptop is restored to the usual . Then the situation repeats, as after a recent connection. A couple of minutes familiarThe numbers keep going, but then they drop anyway. In general, the "normalization" of the speed for a couple of minutes occurs after opening any application on the phone, which requires the so-called data transfer.
This does not happen at night (I have night shifts) and at home.
At home, the Internet generally flies in the region of a hundred Mbit.

We can conclude that the problem is in the daily network load, since I work in a fairly large building, where there are a lot of people. But if that were the problem, wouldn't the speed be consistently low? Maybe the matter is in some non-obvious settings in the phone, which are dependent on the time of day? Why can such miracles happen?

Answer 1

Most likely, the provider cuts with a shaper, tk. sees the distribution.
As far as I know, the megaphone does not have unlimited Internet tariffs. Can you give a link? but there are tariffs with a restriction during the day - and unlimited (conditional) at night ...
Well, or it cuts during the day simply because the network congestion is high at the location ... and at night, respectively, no

Answer 2

There was WiFi from the phone to 2 different laptops of the same brand with the same modules and a tablet. The tablet and one laptop OK the second laptop gave out various, often not reproducible symptoms. Location in a human settlement with a huge number of networks.
Resolved by reinstalling the driver.