Outlook Calendar Issue

so I use outlook I have 4 Lawyer Calendars added so I can view and manage their appointments but everytime I switch out for the calendar view and go check my emails I have 1 personal and 2 work emails, then when I switch back to the calendar view it drops one of my Lawyers and puts my personal calendar in to replace it, it hasn't done it in awhile but now it is and it wont stop, how do I correct this