misty is doing back streching

ffmpeg -ss 07:40.041 -to 07:40.666 -i   'g5s1e08.mp4' -filter_complex '[0:v:0]crop=640/8*8:709/8*8:522:367,split=2[a1][a2],[a2]reverse[r2],[a1][r2]concat=n=2,split=4[s1][s2][s3][s4],[s1][s2][s3][s4]concat=n=4[out]' -shortest -map '[out]' -an -preset slowest misty_is_doing_back_streching.webm

ffprobe 'g5s1e08.mp4' 2>&1 | grep -E 'Stream #0:0.*Video|Duration'
  Duration: 00:23:17.41, start: 0.000000, bitrate: 3780 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 2497 kb/s, 24 fps, 24 tbr, 24k tbn, 48 tbc (default)