Tvheadend mux problem

Hi all, It's about 1 week that i got:
RPI3
Libreelec 7.0.2
Tvheadend 4.1-2369

It's the cool os and pvr i tested, much better than boxes that i have seen from friends or at the shops. As noob i found some problem (as usual ^_^)
More in deep I have this problem (sorry for my bad english):
I configure TVH server via web adding and IPTVauto network, i put my url and i get 175 mux. When tvh start to scan it only 75 go ok, the others fail. Looking into every failed mux i see an url ending with m3u or m3u8 or mp4 or mkv. When i try to play those links with vlc or via firefox (that open vlc) many of those work (90%). Reading around in the net i found that this problem can be solved with the last developer version of tvh. I don't know if the problem can be solved with the developer version but i really wish to try. Anyone can help me?
I will be happy to have some tips about how to recognise the developer version, how to compile an addon for kodi so i can try to do the work by myself ^_^. Any help is welcome. Thanks in advance.

Update 1
if i correct the extension of the mux url from ".mp4" or ".mkv" to ".ts" and setting again in mux configuration "scan status" in "PEND", the mux "scan result" go OK. Anyone got any idea? Can't correct manually 100 mux every update. Thanks in advance for the help.