I read on this support thread that ACF is going to or has already released some JS updates for v5.2.8 to fix compatibility issues with other plugins.
I’m having a lot of trouble with that BNFW plugin too and am wondering if there’s a place on this site I should check for preliminary release files.
You might want to open a new support ticket http://support.advancedcustomfields.com/new-ticket/ and reference that post. I cannot find anything on the forums so I’m assuming that how the other person reported the problem. I’m sure the new file is available on the GitHub repo, but you’ll probably need to submit a ticket to request access to that as well.
In the mean time I will attempt to bring this post to the developer’s attention.
Thanks for the thread.
This issue has recently been fixed and will be included in the next version.