Interesting, you're first that reports this issue.
Game indeed uses a few tricks to record gameplay from secondary camera, as you cannot normally record video in unity, especially in web build. But it was balanced to a reasonable bandwidth (~1.5 mb for 1 second of recording). 5gb/sec sounds ridiculous and indeed looks like something goes wrong.
Does issue persists in desktop build, or it is web only?
Guys, post below if you also have this issue, looks like something i should look at, if it is reproducible en masse.