Well, it tells you all you need to know: Do not use the legacy QT module to encode H.264. AME does a much better job at that.
what is the QT legacy module?
Which one should we be using?
There are multiple things going wrong in your post. First of all, QuickTime's H.264 implementation is terrible and has been abandoned by Apple. If you need an H.264, use the presets in the Adobe Media Encoder for making an H.264. If you need a MOV file, try using a different codec. Without knowing what you're rendering for, I can't give better suggestions.
The second big thing is that you're running a fairly out of date version of AE. You're on 13.0. If you want to continue using CC 2014, I'd recommend updating to 13.2. You get added features and many bug fixes. (You also get the cool new blue color.)
You could also considering updating to CC 2015. Some people have had issues with it due to the halfway done new architecture (although many of those issues have been fixed in the 13.6.1 update). So, in case you too have issues, make sure to CHANGE the default setting to remove old versions (see here: keeping previous versions installed when installing CC 2015 applications) so that you can keep CC 2014 on your system.