Avimux refuses Video Caps

Hey guys,
i developed a pipeline with two parallel streams which are combined in a muxer. There is one audio stream and one video stream. My problem is, that the GstAviMux refuses the following videocaps:
video/x-h264,
            stream-format=(string)byte-stream,
            alignment=(string)au,
            width=(int)1280,
            height=(int)720,
            framerate=(fraction)0/1,
            chroma-format=(string)4:2:0,
            bit-depth-luma=(uint)8,
            bit-depth-chroma=(uint)8,
            parsed=(boolean)true,
            profile=(string)constrained-baseline,
            level=(string)3.1

As i understand the documentation of the GstAviMux element, it should accept this caps. Is there any ideas for this problem?

Kind regards,
Felix Sternkopf