ges-launch: timeoverlay errors

I noticed a few problems in ges-launch:

ges-launch-1.0 +test-clip "blue" start=0 duration=5

will produce a constant stream of error messages from timecodestamper

0:00:06.231966197 10194 0x7fd16802e4f0 ERROR        timecodestamper gsttimecodestamper.c:1012:gst_timecodestamper_query:<timecodestamper0> Need a known, non-variable framerate to answer LATENCY query

This goes away with

ges-launch-1.0 +test-clip "blue" start=0 duration=5 use-time-overlay true

but then this will hang at time 5.

Moreover, with

ges-launch-1.0 +test-clip "blue" start=0 duration=5 set-use-time-overlay true +test-clip "green" start=5 duration=5 set-volume 0.25 set-use-time-overlay true

at time 5, the video will hang (stuck on blue, but audio changes).