Dont do that! Just go to your cinematic, before you copy the level or the cinematics, select everything inside the cinematics, right click and “CONVERT TO SPAWNABLE” (01) - this way the everything inside of it will be on the sequencer itself - then you go ahead and copy the level and copy the sequence.
2 - Open the level, and open the “new” sequence, right click and Convert to Possessable, and then you can change whatever you want inside of it.
Hope it helps.