User A did a email search using Advanced search function in a shared mailbox and User B also did a Advanced search from the same shared mailbox, then user A's search result changed to user B's search query. Any fix for this issue.

Exchange server 2013 and both of them are using outlook online mode and having full permission in that shared mailbox. Accessing as a additional mailbox.

Hi,

Please install the latest patches and service packs for Exchange 2013 to have a try:

https://www.microsoft.com/en-us/download/details.aspx?id=47679

Regards,