One thing that I do know will cause a problem is trying to preview a post that has not been saved. For example, you edit a field and click on the preview link without first saving. The value of the field you just edited will not be save.
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ACF wouldn’t be so widely used in WordPress if it didn’t have some pretty amazing capabilities. In this article, we look at a few of the features we’ll discuss during “7 things you didn’t know you could do with ACF” at #WPEDecode later this month. https://t.co/5lnsTxp81jpic.twitter.com/Yf0ThPG1QG