This pipeline works for a few seconds and then fails:

vid_enc=avenc_mpeg2video
ip=127.0.0.1
port=1235

gst-launch-1.0 -v --gst-debug=3,udpsink:3,multiudpsink:3 \
videotestsrc pattern=smpte is-live=true \
! video/x-raw,format=I420, \
width=720,height=480,framerate=30000/1001 \
! $vid_enc bitrate=4000000 \
! queue \
! mpegtsmux \
! queue name=udpq \
! rtpmp2tpay \
! udpsink port=$port host=$ip sync=true buffer-size=300000

Here a few of the error messages:

(gst-launch-1.0:9876): GStreamer-CRITICAL **: gst_mini_object_unref: assertion `mini_object->refcount > 0' failed

(gst-launch-1.0:9876): GStreamer-CRITICAL **: gst_mini_object_unref: assertion `mini_object->refcount > 0' failed

** (gst-launch-1.0:9876): WARNING **: Unexpected item 02DBA8D8 dequeued from queue udpq (refcounting problem?)

(gst-launch-1.0:9876): GStreamer-CRITICAL **: gst_mini_object_unref: assertion `mini_object->refcount > 0' failed


Here's a simplified pipeline that also prints the assertion messages:

gst-launch-1.0 \
videotestsrc pattern=smpte is-live=true \
! video/x-raw,format=I420, \
width=720,height=480,framerate=30000/1001 \
! $vid_enc  \
! mpegtsmux \
! fakesink

I tried the simplified pipeline on my MinGW (1.0.1) build and on ubuntu (1.0).
I got the same assertion messages in both cases.