Why can't my video play from where I drag the playback bar?
video1 has a very short keyframe interval - it has a keyframe every few frames. video2 doesn't. Some players have the ability to decode upto non-KF silently and start playing from seek point. If yours doesn't, then it will start from the nearest keyframe preceding the seek point.

ffprobe origin.mp4 -show_entries frame=key_frame,pkt_pts_time -select_streams v -of compact=p=0 | grep ame=1


Result:

key_frame=1|pkt_pts_time=0.000000
key_frame=1|pkt_pts_time=0.333667
key_frame=1|pkt_pts_time=0.667334
key_frame=1|pkt_pts_time=1.001001
key_frame=1|pkt_pts_time=1.334668
key_frame=1|pkt_pts_time=1.668335
key_frame=1|pkt_pts_time=2.002002
...
key_frame=1|pkt_pts_time=32.699366
key_frame=1|pkt_pts_time=33.033033
key_frame=1|pkt_pts_time=33.366700
key_frame=1|pkt_pts_time=33.700367


Video2:

ffprobe my.mp4 -show_entries frame=key_frame,pkt_pts_time -select_streams v -of compact=p=0 | grep ame=1


Result:

key_frame=1|pkt_pts_time=0.000000
key_frame=1|pkt_pts_time=2.293958
key_frame=1|pkt_pts_time=5.171833
key_frame=1|pkt_pts_time=7.257250
key_frame=1|pkt_pts_time=9.718042
key_frame=1|pkt_pts_time=13.221542
key_frame=1|pkt_pts_time=15.473792
key_frame=1|pkt_pts_time=21.271250
key_frame=1|pkt_pts_time=24.357667
key_frame=1|pkt_pts_time=29.195833
key_frame=1|pkt_pts_time=32.407375




Add -g 8 to ffmpeg transcode command to place a keyframe every 8 frames.