Turning off "Show in Groups" does not solve the problem in my case; the jumping continue. I would regard that as a "Band-Aid" rether than a solution anyway. "Show in Groups" is very useful and disabling it is not an acceptable solution in my opinion.
MICROSOFT,PLEASE PAY SOME ATTENTION TO THIS AGGRAVATING BUG.
I thought turning it off worked but it was only for one instance.
It is definitely only happening to me when I change from any folder back into the INBOX folder and try to scroll using the scrollbar arrow up, down or clicking a point on the bar. For example if I'm in the deleted folder and click back into the INBOX
then click the either arrow, the focus will automatically select roughly the middle message on the scroll bar... If you are past that message in the list and repeat this it will not do it. Only when in the upper probably 2/5 of the bar... I'm sorting by date
with newest on top showing ALL messages. Grouped by Date but no Conversation Mode...
Sporadically when I delete a message from the INBOX it seems to simulate the same thing but I'm trying to replicate that.
I have 5 other user accounts that show up on my folder tree that I manage and none of those have the issue when going from any folder back to their corresponding INBOX...
So Microsoft... It's something about when refocusing on the Primary INBOX on Office365 Exchange with Outlook 2016 scrollbars don't understand how to take the current position and translate that to the starting position in the click... IDK... Just a geek!
***UPDATE*** It also happens when using the keyboard arrow keys as well as the scroll wheel on the mouse... so fix your starting position MS!
Also, I'm on a PC so this really isn't exactly the same thing I came to find out... LOL