What causes FFmpeg to break a video file when saving from a hls stream?

Question

fmpeg

There is a script on the windows server that copies the hls stream of live broadcasts and saves it to mp4, but if you leave the script for a long time (~ 1 hour) without monitoring the output, instead of a fully recorded broadcast, "broken" recordings ~ 350mb appear + a strange feature is not yet right-click on the file->Property its weight in the system is shown as 0 bytes
Perhaps someone knows the reason.

Answer 1

Solution:
The donor site checked some kind of payment and did not allow one of the stream blocks to be loaded
[https @ 0000027daf2b2a80] HTTP error 402 Payment Required
[hls @ 0000027dae5f7e40] Failed to open next segment 1696 of playlist
0 mp4 does not withstand any emergencies, it simply broke, changing to mkv helped, now all records are stably saved and read even with HTTP error 402 Payment Required.
Thanks to all!