USE CASE : A team share a shared mailbox, This shared mailbox is mapped to their own Outlook Client in cache Mode, Now user A update the shared mailbox with folder and emails but others users do not see the updated content and folder in their outlook.
This issue was covered by the Microsoft in the following KB.
Below the little summery what is there in this article, you can probably go through the same for the deep understanding.
Root cause pointed was to cache mode enabled for the shared mailbox when attached to users own outlook profile, so disabling the same for the Shared mailbox is suggested on this article, one more solutions is suggested, which is to configure the shared mailbox outlook profile separately.
The reason behind the same mentioned by the Microsoft is that when you map a shared mailbox to your own outlook profile all the folder in the mailbox counted under your own mailbox folder policy so if it reaches the high no of folder combined in the outlook may case the issue.
I also found few TechNet forum article where disabling the auto map for shared mailbox also have fixed the issue.