Hi Precision Creations – My version of ACF Pro updated automatically to v5.3.8 so before I rolled it back I thought I would try a few things. One of which was to try things in a different browser.
I have just switched browsers from Chrome to Safari and that strangely seems to have fixed the issue for me. However it was still not working in Chrome, even after I clearer the cookies.So I wiped ALL the browsing data completely and that has fixed the issue for me on Chrome.
I still want to do some further testing but perhaps you can try that too.
