How to track the video slowdown in the player (in which player is this possible) for the end user?

Question

JW Player

Good afternoon, dear experts!
I would be very grateful for your interest in this issue. :)
Users watch paid video content that is served from a single server.
Complain that it slows down.
Currently using JWPlayer
I wanted to be able to detect when a video is slowing down.
Advise!