Last weekend I found out that my two recent exported MP4 files aren't working so well with Adobe Premiere Pro CS6 anymore. Importing takes a while, previewer show only green footage and I tested it on several computers with CS6 (Different OS and GPU Drivers), all with the same problem.
Weird enough, those two files do work in Adobe Premiere Pro CC. I hope Action's MP4 exports will still support Premiere Pro CS6 and that this scenario a bug is. (File sizes of AVI are huge compared to MP4, so it makes a difference.)
Thank you for your time.