Strange bug re-encoding video with GST 1.8.1 on Mac OS 10.10

[Andy Robinson]

GST 1.8.1 on Mac OS 10.10

Hello,

Here are commands for copy-and-copy-again of a video:

gst-launch-1.0 filesrc location=Bear.wmv ! decodebin ! videoconvert ! 
x264enc bitrate=1280 ! mp4mux ! filesink location=out1.mp4

gst-launch-1.0 filesrc location=out1.mp4 ! decodebin ! videoconvert ! 
x264enc bitrate=1280 ! mp4mux ! filesink location=out2.mp4

On Windows 10, GST 1.8.1, this works fine. But on Mac OS 10.10 the first 
copy succeeds but the second one produces this:

Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Redistribute latency...
Got context from element 'vtdechw0': gst.gl.GLDisplay=context, 
gst.gl.GLDisplay=(GstGLDisplay)"\(GstGLDisplayCocoa\)\ gldisplaycocoa0";
ERROR: from element 
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstQTDemux:qtdemux0: 
GStreamer encountered a general stream error.
Additional debug info:
qtdemux.c(5423): gst_qtdemux_loop (): 
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstQTDemux:qtdemux0:
streaming stopped, reason not-negotiated
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...

For completeness I have placed the source file Bear.wmv here:
http://www.seventhstring.com/other2/Bear.wmv
though my impression is that this problem happens with pretty much any 
video.

Using GST 1.6.3 there is again no problem on Windows but on Mac both 
copies appear to succeed: however the second copy won't play, QuickTime 
Player says the file is corrupt.

Any suggestions for a fix/workaround/whatever would be appreciated.

Regards,
Andy Robinson, Seventh String Software, www.seventhstring.com