Understand stalled / queued connection

Hello,

I have a test wydarzenia.interia....Milan, Italy - EC2 - WebPageTest Result

There is some stalled / queued request such as https://js.iplsc.com/inpl.uanc/1.3.31/35.inpl.uanc.js.

On the waterfall, we see this request at position 58. I’m also log the netlog in that test.

From the netlog we can read that this request is blocked by ResourceScheduler

Anyone know how we can determine how resources are scheduled ?

How determine which another resources cause that this one is stalled / queued ?