Why does FFmpeg stop streaming?

Question

fmpeg

I have a python script that runs a script to run ffmpeg, the command is:

ffmpeg -stream_loop -1 -i stream.mp4 -stream_loop -1 -i music.m4a -shortest -map 0:v:0 -map 1:a:0 -acodec aac -pix_fmt yuv420p -vcodec libx264 -b:v 500k -crf 35 -intra-refresh 1 -g 1 -filter:v "scale=-1:720, drawtext=textfile='mytext.txt':x=0:y=0:fontsize=24:fontcolor=white:reload=1" -r 15 -preset ultrafast -tune zerolatency -err_detect ignore_err -truncate 0 -f flv "rtmp://moscow.restream.io/live/***"

Stream stops very often https://vk.com/videos-204599935