Thank you for your reply. I have not tried what you suggested because Exchange admin access is controlled by a different team and not by Desktop Support. A little silly.
I brought the issue to our MS Office admins and they suggested I check the "Delegate Access" from the user who is sharing their Mailbox instead of removing and readding the permissions.
Also, while walking into work today I found out the user who was experiencing issue was terminated and from my understanding no other EA is having similar issues, so this Question can be considered "Resolved."