Glad I found this post... I am also living this issue at the moment. I have a couple of known problem channels. If I map them and then play from the Guide, the bandwidth will drop from 18,000kbps to near nothing every say 30s, resulting in freezing and stuttering. If I play the corresponding mux directly, the bandwidth will hold steady at 18,000kbps and life is good. I can then go back and play ANY channel in the Guide without experiencing bandwidth issues. I still get several continuity errors here and there, but they don't seem to affect stream quality. I need to repeat this work-around each time I reboot.
I have reproduced this issue across two hardware installs (inexpensive mini-pc and a desktop-pc) with LibreELEC with Tvh-addon v9.2.0.123, using both wintv-hvr-950q and 955q. Playback/stream testing on VLC desktop, and the phone using TVH app.
Have you been able to find the cause and/or a permanent fix?