How do I to get consistent takes when Rendering?

I’m using Sequencer to try and render the MetaHumans scene. I want to record it 4 times with 4 different lighting states and then view all of these side by side later. I feel like I’ve got Sequencer all worked out but when I get to putting the videos together later I realise none of them are the same length! They range from 46 secs to 1 min. Playing them side by side by 4 secs in there is already a noticeable disconnect between them. I can only imagine this is a rending issue. Is there a way to make them render consistently?