This doesn't appear to be a regression in the most recent CodeMirror merge - I can repro it in the commit right before it.
Also, the blank-at-bottom issue seems to be more obvious when opening a large Quick Docs item (e.g. "background") in a long CSS file.
@njx I can reproduce it only when I hit Esc immediately before inline Editor animation is done in step 3.
I think I can repro even if I wait a bit, but it does seem likely to be a race condition of some kind. That doesn't really explain the "blank lines at bottom" issue, although that's probably also related to the animation timing.
I have another scenario that can cause the page to scroll to the bottom and won't let you scroll back to the top of the page. But you need to have a css file like dropzone.css in your project. Once that css is in your project sometimes opening the inline editor on any tag will show up css code from dropzone.css. And if you dismiss the inline quickly, then the hair cursor in the main editor is set to a line in the bottom portion of the page and you won't be able to scroll up.
Update: dropzone.css has to be the minified version and you have to dismiss the inline quickly to see it on mac. I pressed Cmd-E twice to reproduce it consistently.
That sounds bad. Does it repro before the latest CM merge?
Yes, it does reproduce even without the latest CM merge.
Changing to medium priority to look at @RaymondLim's case.
Nominating for 1.0.
Reviewed. Keeping for 1.0 to investigate the issues and figure out how important/difficult to fix they are (and if the problems still exist with CMv4)
Reassigning to @RaymondLim - feel free to reassign
@njx I'll be closing this since I can't reproduce the odd behavior in the master anymore and I believe changes in CMv4 or later have fixed the scrolling or rendering issue.