Display name - surname all caps?

Hi, not a massive problem but having recently moved to Exchange online I am getting some odd capitalization on our users.

I have had a look and cannot see anything different in the admin centers for the affected users. It is not affecting all users, just odd ones here and there.

For example, my user display name is set to Eddie Wright, my email address is ewright@domainname.com  and Outlook shows my details in auto-complete exactly the same. 

I have another user, let's say John Doe with email jdoe@domainname.com  who is shown as John DOE in Outlook auto-complete even though the display name format in the admin center is the same as for me.

If I add the user from the address book it shows the correct capitalization but if I hover over the email address the pop up box shows the surname is all caps again.

As I say, it is not a major problem, but I am getting some users asking why their name is shown differently from others and one of the affected users is my CEO......

Many thanks for any pointers, Eddie