Mailboxes Disappear from Favorites

With no apparent reason and very sporadic. I will close the mail application and all of the mailboxes I had placed on my favorites bar will be gone. Additional, the organization of my inboxes changes and puts iCloud on the top again.

I can not figure out what if anything I'm doing to cause this, but having to recreate my favorites bar what seems like weekly, is getting old. Anyone else having this trouble?

Thanks for the help.