FFmpeg transcoding video H.264 -> AV1 leads to distorted image

Question

I'm reading video from stdin via pipe similar to this one Python gets stuck at pipe.stdin.write(image.tostring())

FFmpeg is using libsvtav1 codec with options according to documentation

ffmpeg -y -f rawvideo -i pipe:0 -s {frame_width}x{frame_height} -r {frame_rate} -c:a copy -c:v libsvtav1 -preset 6 -crf 30 -svtav1-params "color-format=1:film-grain-denoise=0:mbr=2M" {output_file} 

Here's couple of details about used FFmpeg version as well as input video

ffmpeg version n5.1.3-14-ge5b5dd6653-20230621 Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 13.1.0 (crosstool-NG 1.25.0.196_227d99d)
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-ffbuild-linux-gnu- --arch=x86_64 --target-os=linux --enable-gpl --enable-version3 --disable-debug --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-openssl --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libpulse --enable-libvmaf --enable-libxcb --enable-xlib --enable-amf --enable-libaom --enable-libaribb24 --enable-avisynth --disable-chromaprint --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --disable-openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --disable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libdrm --enable-vaapi --enable-libvidstab --enable-vulkan --enable-libshaderc --disable-libplacebo --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags=-pie --extra-libs='-ldl -lgomp' --extra-version=20230621
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, rawvideo, from 'pipe:0':
  Duration: N/A, start: 0.000000, bitrate: 331776 kb/s
  Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1280x720, 331776 kb/s, 30 tbr, 30 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> av1 (libsvtav1))
Svt[info]: -------------------------------------------
Svt[info]: SVT [version]:   SVT-AV1 Encoder Lib v1.5.0-12-g0f8b3a81
Svt[info]: SVT [build]  :   GCC 13.1.0   64 bit
Svt[info]: LIB Build date: Jun 20 2023 23:48:14
Svt[info]: -------------------------------------------

The output video transcoded by SVT-AV1 codec is blemished as you can see on the images below. Normally I would say it could be caused by wrong pixel format, but input stream has yuv420 format what is the same as encoder's pixel format parameter --color-format.

Please share your experience or ideas how to get it transcoding correctly.

Thanks in advance.