4K video from Panasonic VC8xx broken?
Yes, the videos are broken. They are created due to an overheat and some kind of built-in reduction of the recorded video to FullHD; but the resolution of the result is still 4K, and the last filled content of the 4K buffer is used to fill the bottom large part (hence the repeating).

Still, it's possible to get a FullHD video from the broken file:

FILTER='
[in] split [a][b]; 
[a] crop=1920:540:0:0 [ac]; 
[b] crop=1920:540:1920:0 [bc]; 
[ac][bc] vstack [stack];
[stack] il=luma_mode=interleave:chroma_mode=interleave'  

if [ "$2" != "" ] ; then
  ffplay -i "$INPUT" -vf "$FILTER"
else
  set -x
  ffmpeg -i "$INPUT" -filter:v "$FILTER" $QUALITY_GOOD_H265 -c:a copy "$NEW_NAME" \
  &amp;&amp; touch "$NEW_NAME" -r "$INPUT"
  set +x
fi