Viewing HTML in the Redactor editor causes scroll bug [Chrome/Opera].

[mattkatt]

Describe the bug
When viewing the HTML in the Redactor editor, scrolling to the bottom of the page prevent scrolling back up - most likely caused by javascript, possibly Redactor's own script. Does not occur on Firefox or Edge.

To Reproduce
Steps to reproduce the behaviour:

1. Go to 'Create/Edit' on any section that uses the Redactor editor.
2. Fill the text area with enough content to cause the page to be larger than the window.
3. Click on 'HTML' in the Redactor bar.
4. Scroll down to the bottom of the page.
5. Attempt to scroll back up the page using arrow keys, scroll-wheel or by dragging the scroll-bar.

Expected behaviour
Page to scroll as normal.

Desktop (please complete the following information):

• OS: Windows 10, using Homestead VM.
• Browser: Chrome 71, Opera 57
  (Cannot check Safari at this moment in time)

Additional context
I believe this is actually caused by the Redactor function _doFixed, found on line 12129 of redactor.js, but I cannot see anything that would call this function directly. Please note this is happening on both my customised version of the CMS view blades (which includes some extra JS), AND with the default included views and JS.

[mlantz]

I'll look into fixing this, sorry for the delay