1) Launch program, open rootfly file (zooming with mouse wheel works as expected)
2) Click the Annotate button and click OK on the Annotate dialog box (doesn't matter what is checked in the box). Zooming with the scroll wheel no longer works. At this point you can change sessions and windows, and scroll-zooming still does not work
3) Click on what apparently is any other control on the window (i.e, inside a Read-only Properties text box, uncheck Show Diameters, click a zoom button, etc.). At this point, scroll-zooming functionality seems to be restored. As far as I can tell, it is only broken immediately after clicking the Annotate button and clicking OK in the Annotate dialog.
I have since discovered that you do not even have to click another control on the screen; you can bring the focus to another program running in windows, bring the focus back to rootfly, and scroll-zooming works as expected.
Still broken in 1.8.36.