How to prevent ffmpeg from dropping frames when trimming?
Try to place the -ss and -to after the input: 

ffmpeg \
  -i input-original.mp4 \
  -ss 00:11:42 \
  -to 01:11:22 \
  -c copy \
  output-trimmed.mp4


According to @Gyan (https://stackoverflow.com/questions/45004159/ffmpeg-ss-and-t-for-cutting-mp3)


  When -ss and -t are placed before the input, ffmpeg resorts to fast
  seek which relies on the index of the input to allow ffmpeg to start
  and stop seeking. MP3s don't have indices, so ffmpeg estimates
  duration via bitrate. This can be inaccurate.
  
  When -ss and -t are placed after the input, ffmpeg counts demuxed
  packets. This will be accurate.


If it doesn't work you can also try to convert your video to intra-frame format (try ffvhuff), trim it and then convert it back to mp4 but this will slightly decrease the quality of the trimmed output. Keep in mind that ffvhuff will create huge file in size so make sure you have enough free space if you want to go this way.