Office 365 Mailbox folders sync issue with Android & iPhones

Come across a number of issues with mailboxes with either a large number of folders under one folder, Inbox for example, or with multiple nested folders.
But the latest I had involved a user with about 60+ folders under her Inbox. She complained that once I migrated her mailbox to Office 365, on her Android phone when navigating to "Show all folders" under her Inbox, she could only see about 4. This was the same on her iPad. The ones viewable have been newly created since migration.
Digging around I found the issue and solution.

Issue
When doing a "normal" migration, setting up the mailbox and PST'ing the data into it, there is some kind of flag attached to the folder. As a result this folder will not sync. To test I tried to create a new folder and this was view able from the Android handset. This is because the flag attached to the new folder is now different under the Office 365 environment.

Fix
You have to do the following;

1. Pick a folder and rename it with "OLD" tagged to the end of it.
2. Create a new folder with the same name, except for the "OLD" bit. 
3. Move all the mail from the "OLD" folder into the newly created one. 
4. Delete the folder with "OLD" tagged at the end. 

Low and behold this worked. Took me three hours to do this on this users particular mailbox. I have the same issue with another that has even more folders. 

This handset was running the latest version of Android so this is most defiantly an Office 365 problem.