Also relating to gopro proxy, the change made here to fix gopro’s bad .lrv aspect ratio is being kept even after disabling proxy usage and after exporting thus the output has a few black pixels of padding at top and bottom.
I see the .mlt has this line for all videos that had gopro proxy, luckily it’s easy to find+replace it away.
<property name="force_aspect_ratio">1.00629</property>