Had a lot of typo mistakes in the first post, edited it. Sorry about that, was a bit tired at the time.
Tried to repro this in the incognito mode, it doesn't happen there, but for whatever reason I am unable to turn on overlay page controls. I also don't think this is an issue with missing portions of a website as I don't see anything different at all and all of the functions (that I use, at least) seem to work fine.
Anyway, I went on to investigate it back in the default browser mode and noticed errors are generated on overlay activation. If I turn it off (or navigate pages without touching mouse), I get no errors and everything seems to be fine. I didn't notice at the time, but this could've been deduces from JS screenshot I sent earlier: errors happen in some overlay handler code -- strings give away it. As I mentioned in the first post, the amount of errors rises with every chapter change. Rising number of errors looks to me like a bug with repeated callback registration on the same "event". No idea what's causing errors in the first place.
Here is quick video I made to illustrate:
https://files.catbox.moe/flhy1j.mp4