log level debug causes command to work

[certaindestiny]

Summary of the bug:
How to reproduce:

ffmpeg  \
-loglevel debug \
-fflags nobuffer \
-f x11grab \
-i :$DISPLAY \
-f alsa \
-i hw:11,1 \
-ac 2 \
-ar 48000 \
-vf interlace=scan=tff:lowpass=complex,scale=1920:1080 \
-pix_fmt uyvy422 \
-format_code Hi50 \
-f decklink \
-top 1 \
-flags:v +ildct+ilme \
-r 25000/1000 \
  "DeckLink Quad ($SDIO)" #2>1 >/dev/null &
ffmpeg version
built on Ubuntu 18.04

ffmpeg version N-100906-gad2cc0e2f4 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
  configuration: --prefix=/root/ffmpeg_build --pkg-config-flags=--static --extra-cflags='-I/root/ffmpeg_build/include -I/root/ffmpeg_sources/BMD_SDK/include' --extra-ldflags=-L/root/ffmpeg_build/lib --extra-libs='-lpthread -lm' --bindir=/root/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree --enable-decklink --enable-libxcb
  libavutil      56. 64.100 / 56. 64.100
  libavcodec     58.119.100 / 58.119.100
  libavformat    58. 65.101 / 58. 65.101
  libavdevice    58. 11.103 / 58. 11.103
  libavfilter     7.100.100 /  7.100.100
  libswscale      5.  8.100 /  5.  8.100
  libswresample   3.  8.100 /  3.  8.100
  libpostproc    55.  8.100 / 55.  8.100
Hyper fast Audio and Video encoder

For some reason whenever i execute the above command without loglevel debug the command hangs. when trying to troubleshoot with the debug command it is running fine and without any problems except for the overhead of the extra logging.
I am in no way capable to troubleshoot why this might be happening but if any information is required id be glad to provide.
Some extra info:
SDI card=Decklink Quad2
happens on all SDI outputs =yes
happens without audio input =seems not to for some reason.
$display and $GPIO are pushed from other scripts but can be hardcoded to be display :11 and GPIO 1-7.

[certaindestiny]

Output after starting command:

[x11grab @ 0x55deaef9d500] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, x11grab, from ':11':

Duration: N/A, start: 1612292759.605620, bitrate: 1988667 kb/s

Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1920x1080, 1988667 kb/s, 29.97 fps, 1000k tbr, 1000k tbn, 1000k tbc

Guessed Channel Layout for Input Stream #1.0 : stereo
Input #1, alsa, from 'hw:11,1':

Duration: N/A, start: 1612292759.616126, bitrate: 1536 kb/s

Stream #1:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s

Stream mapping:

Stream #0:0 -> #0:0 (rawvideo (native) -> wrapped_avframe (native))
Stream #1:0 -> #0:1 (pcm_s16le (native) -> pcm_s16le (native))

Press [q] to stop, ? for help

output after stopping
x11grab @ 0x55deaef9d500] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
[alsa @ 0x55deaefa8380] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
Finishing stream 0:0 without any data written to it.
Finishing stream 0:1 without any data written to it.
[decklink @ 0x55deaefce480] Found Decklink mode 1920 x 1080 with rate 25.00(i)
Output #0, decklink, to 'DeckLink Quad (1)':

Metadata:

encoder : Lavf58.65.101
Stream #0:0: Video: wrapped_avframe, uyvy422(top first), 1920x1080, q=2-31, 200 kb/s, 25 fps, 25 tbn
Metadata:

encoder : Lavc58.119.100 wrapped_avframe

Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Metadata:

encoder : Lavc58.119.100 pcm_s16le

frame= 0 fps=0.0 q=0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed= 0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)
Exiting normally, received signal 2.

[certaindestiny]

After some troubleshooting done in the IRC it was fixed by including -frame_rate 50 on the input side.

still weird that it works with the debug flag set