From https://groups.google.com/d/msg/mozilla.dev.platform/zdOIK5fxmFA/4xXp4K0XCwAJ ---- 1. Reader mode's toolbar now sometimes seems to jump up and down several times. ---- It seems like there's some interaction with the dynamic toolbar and the reader mode toolbar that's causing it to show/hide a lot. Need to investigate what's going on here.
Just a thought: It may be the case that reader mode always had this issue, but it just wasn't triggered until the scrolling changed. Basically, reader's toolbar might a bit too sensitive in showing up. Disclaimer: I'm wildly speculating based on usage of Firefox for Android, with no factual evidence to support this guess.
It looks like reader mode no longer has a toolbar, there's a floating Aa button which brings up a settings pane.