Почему скорость передачи данных с сервера снижается во время потока?

Why is the data transfer speed from the server being cut during the stream?
12 minutes ago|LINK|95.79.163.30

There is an ASP. NET application running on a VPS server. (Channel width 200 mb \ s). It works as follows: data is transferred from the client to the server and immediately to the browser (about 1.5 mb / s). When I run on IIS Express everything works as expected, but when sending to a remote server, the send speed is cut, while the receive speed remains at the level of (1.5mb / s).

There is only one answer - the problem is in the VPS server, but as soon as I stop sending data, the sending speed rises to the desired 1.5 mb / s. I have been struggling with the problem for several months now. I changed the hosting provider but does not help. What's the matter ??

SignalR is used for data transfer (with Forced use of WebSocket). The site is hosted on IIS.

After searching for answers in other forums, I came to the conclusion that the problem is in SignalR.
 
Here is the code, the code that is on the sender client (1st picture)

On the Hub (Fig. 2)

On the JS client - the recipient.
Can you advise something.

1) https://drive.google.com/open?id=1hUqBnNpm5-R3Jk4vD7OeEnO0ZsA0uaNh

2) https://drive.google.com/open?id=1hUqBnNpm5-R3Jk4vD7OeEnO0ZsA0uaNh

3) https://drive.google.com/open?id=1hUqBnNpm5-R3Jk4vD7OeEnO0ZsA0uaNh

Tried different VPS configurations. Up to 5 cores, 10 GB of RAM and 1 GB / s channel width. Even on the most powerful configuration, the problem is the same.