Hi elliot,
I am using Getshopped (WP E-commerce) and I found what the problem is. Getshopped automatically generates an metabox for metadata. So on my edit page are 2 boxes for metadata. one from Getshopped, one from ACF. The problem is that Getshopped overwrites the data of ACF. I assume it saved after ACF saves.
Is there a way for ACF to make sure it saves last?
Hope to hear from you.