video – Compressing an MTS file to MP4 gives error in QuickTime

I have a long video file that I want to trim, resize, and compress with H264:

ffmpeg -y -ss 1.2 -to 2:03.800 -i long.MTS -vcodec libx264 -vf scale=320:-1 -vb 500k short.mp4

The file plays in VLC and not in QuickTime with this error:

The document could not be opened. An unknown error occurred (-50).

The same thing happens with the .mov container. The problem is that basic users are unable to see the compressed movie, and the original movie is too heavy to share.

The version of ffmpeg is 4.3.1, the version of macOS is 10.14.6, both up to date. ffprobe on the .mov file returns:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '':
    major_brand     : qt  
    minor_version   : 512
    compatible_brands: qt  
    encoder         : Lavf58.45.100
  Duration: 00:02:02.92, start: 0.000000, bitrate: 902 kb/s
    Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p, 320x180 (SAR 1:1 DAR 16:9), 501 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
      handler_name    : VideoHandler
      encoder         : Lavc58.91.100 libx264
    Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1(side), fltp, 394 kb/s (default)
      handler_name    : SoundHandler

How can I compress, scale, and trim a video from MTS?