GStreamer Editing Services concatenator.c example

I’m writing here for an increased visibility and your help. The concatenator.c example from GES project seems to behaving incorrectly. I’ve added a comment to gitlab issue here although it is already closed. The code is definitely broken but even simple fix does not help. More details here: example concatenate.c hangs (#45) · Issues · GStreamer / gst-editing-services · GitLab

Would someone be able to comment here and provide some hints what’s wrong and how it could be fixed? TIA.