I’ve just recently fixed a bug in the preview logic which may fix the issue you are experiencing!
If possible, can you please download and test the latest build of ACF PRO?
1. Login to your account online: http://www.advancedcustomfields.com/my-account
2. Click on the ‘see all versions’ link next to your license
3. Download the latest 5.4.6-RC2 version
Please let me know if this fixes the issue or not