Hi @iamrobertandrews ,
Thanks a lot for reaching out to us.
ACF PRO was built from the bottom up once more thus it stores the fields and the values differently from the original way in in ACF 4 and below.
This is the reason for the database upgrade as it now has to save to the fields using the new format.
Kindly have a look at this article it should give you more details on the same.
https://www.advancedcustomfields.com/resources/whats-new-version-5/
https://www.advancedcustomfields.com/resources/upgrading-v4-v5/
I hope this helps.
