I had an issue with a couple of users where Outlook would freeze whenever they accessed the public folders. One was on Outlook 2013, the other was on Outlook 2016.
I couldn’t find the exact cause of the issue but a fix that did seem to work was to enable “Download Public Folder Favorites” within Outlook.
I ultimately then set this via Group Policy to enforce the settings for all users.
User Configuration, Policies, Admin Templates, Microsoft Outlook 2013/2016, Account Settings, Exchange, Cached Exchange Mode, Download Public Folder Favorites = Disabled
Another solution to throw in top the mix is turning off the search index for Outlook in the control panel.