Yes, this is a valid approach.
Since it is reproducable as you said, it make sense to debug log the tvheadend like
You can live watch the output using sudo journalctl -f|grep -i tvheadend or redirect the output into a file since there are tons of information.
Perhaps, here you can find more information what happens to tvheadend so the stream starts stalling.
This is the htsp configuration in my tvheadend
If there is no progress by other information here, I suggest you continue searching for help at https://tvheadend.org/ but let’s first see what you can find out.