We are trying with vappi and we cannot reproduce the bug. This is the pipeline
that we are using:

gst-launch-1.0 videotestsrc ! video/x-raw,width=800,height=600,framerate=60/1 !
timeoverlay  ! videoconvert ! vaapih264enc ! video/x-h264,profile=main !
h264parse ! vaapih264dec ! vaapisink sync=0 --gst-debug=*:3

To sumarise

ENC -> DEC : Result

sw    -> sw    : OK
sw    -> omx   : OK
sw    -> vappi : OK
omx   -> sw    : OK
omx   -> omx   : FAIL
omx   -> vappi : OK
vappi -> sw    : OK
vappi -> omx   : OK
vaapi -> vappi : OK