Outlook for Mac Reading Pane problem

Hello,

I've been using Outlook for Mac 2015 with Office 365 subscription since its release. After upgrading it to version 15.6, I start to experience reading pane problem at Mail section. 

Normally, I prefer reading pane to be off. But whenever I switch to Calendar section and go back to Mail section, I see that reading pane appears at the bottom of the mail list. When I click to View/Reading Pane menu, I see it still set to Hidden. To resolve the issue, I need to set it to Right and then Hidden.

Problem occurs everytime I do Calendar / Mail switch.

Kind regards

Erdem