Unknown activity on agents?

We’ve got some unknown events to happen on agent which do not happen in real browser.
Please, see the attachment.
There are unknown events coming to our handler in the agent which is in docker. There are no such events (or they go faster?) in a real browser.

What are the events that could come from wpt agent?

How to delete this post of mine? We found it is not about WPT. There is an issue in 3rd party lib.