FFmpeg freezes on the same frame and gets stuck on it

Question

I'm trying to figure out why the following ffmpeg (4.2.1) command, which works well most of the time, sometimes ends up stuck on the same frame.

This ffmpeg command allows me to make a LIVE streaming with recording VOD at the same time.

Has anyone ever had this problem?

Thank you in advance for your help.

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17:27:07 | ffmpeg.exe -hide_banner -y -rtbufsize 500M -f dshow -s 1280x720 -i video="Microsoft® LifeCam Studio(TM)":audio="Microphone (Realtek(R) Audio)" -flags +global_header -c:v h264   -pix_fmt yuv420p -profile:v baseline -level 3.0 -preset ultrafast -pix_fmt yuv420p -b:v 1935k -r 30.0 -c:a aac -b:a 128k -ac 1 -f tee -map 0:v -map 0:a "'C:\Users\xxx\2020-06-10_17-27-07.mp4'|[f=fifo:fifo_format=flv:drop_pkts_on_overflow=1:attempt_recovery=1:recovery_wait_time=1]rtmp://xx.xx.xx.xxx:1935/live/xxxx" 



17:27:09 | [frame=   39 fps=0.0 q=15.0 size=N/A time=00:00:00.95 bitrate=N/A dup=23 drop=0 speed= 1.9x    ]

17:27:10 | [frame=   54 fps= 54 q=22.0 size=N/A time=00:00:01.44 bitrate=N/A dup=23 drop=0 speed=1.43x    ]

...

17:30:09 | [frame= 5418 fps= 30 q=22.0 size=N/A time=00:03:00.44 bitrate=N/A dup=24 drop=0 speed=   1x    ]

17:30:10 | [frame= 5430 fps= 30 q=20.0 size=N/A time=00:03:00.95 bitrate=N/A dup=26 drop=0 speed=   1x    ]

17:30:10 | [frame= 5447 fps= 30 q=23.0 size=N/A time=00:03:01.44 bitrate=N/A dup=28 drop=4 speed=   1x    ]

17:30:11 | [frame= 5463 fps= 30 q=23.0 size=N/A time=00:03:01.95 bitrate=N/A dup=28 drop=4 speed=   1x    ]

...

17:48:55 | [frame=39141 fps= 30 q=21.0 size=N/A time=00:21:44.46 bitrate=N/A dup=40 drop=15 speed=   1x    ]

17:48:55 | [frame=39176 fps= 30 q=12.0 size=N/A time=00:21:45.43 bitrate=N/A dup=60 drop=15 speed=   1x    ]

17:48:55 | [frame=39199 fps= 30 q=12.0 size=N/A time=00:21:46.20 bitrate=N/A dup=82 drop=15 speed=   1x    ]

17:48:56 | [frame=39205 fps= 30 q=18.0 size=N/A time=00:21:46.40 bitrate=N/A dup=82 drop=38 speed=   1x    ]

17:48:56 | [frame=39205 fps= 30 q=18.0 size=N/A time=00:21:47.22 bitrate=N/A dup=82 drop=38 speed=   1x    ]

17:48:57 | [frame=39205 fps= 30 q=18.0 size=N/A time=00:21:47.73 bitrate=N/A dup=82 drop=38 speed=   1x    ]

...

18:01:05 | [frame=39205 fps= 19 q=18.0 size=N/A time=00:33:56.24 bitrate=N/A dup=82 drop=38 speed=   1x    ]