Why can there be so many 499 errors?

[firecast.gg]

Why can there be so many 499 errors?

[marcroberts]

I’m seeing this too, a lower volume of traffic but a higher percentage of 499 errors

Excessive HTTP 499 errors

A small update here: We’ve had a few more members complaining of similar connectivity problems. Many of them seem to be on the EE network, and for these members I’m not seeing any POST requests getting through to us. Their GET requests are coming through fine though I am seeing in the dashboard analytics HTTP 499 errors on the paths that our app is attempting to call

Any similarities here?