Set sequencer playback position to frames before current frame

Hi,

I tried to use blueprint triggers to control the sequencer playback time. Like when I enter trigger A, it will set playback position at 10s and play, while entering trigger B will set playback position at 30s and play.

The problem is when my current playback position is 30s, and when I enter trigger A and want to go back to 10s, the scene will just become black, with some particles playing. Until I move and enter trigger B it will set the correct scene. There is some load persistent level action before 10s, but not after 10s.

Any idea please? Thanks!