When you have problems with Views not sticking or seemingly disappearing only to come back hours later, you may have corrupt views. You can use the /cleanviews switch to delete all custom views and reset the default views.
At the Start menu, Run command, type
In some cases, you will need to use the full path to Outlook.exe.
A list of command lines is in Outlook's Help, with some additional command lines for older versions of Outlook in the Microsoft Knowledgebase. Search for cleanviews to find the list for your version.
For more command lines:
How to use Outlook's Command line switches (for Outlook 2003, but most commands work in all versions.)
Published July 7, 2004. Last updated on June 16, 2017.