What view mode are you using in the reader?
Tested on Firefox (Linux) with uBlock and it works fine in long strip mode. Scroll to bottom, click on next chapter, get the chapter gap warning, click continue, next (uploaded) chapter loads as expected.
I tried switching to single-page mode to see if that made a difference, but then I didn't even get the "next chapter" button at the bottom. Clicking to advance the page did nothing. Though I'm pretty sure the chapter gap warning not working in single-page mode is a known bug, I'm almost positive I've seen reports of it before.