Trouble with editing

 In this section of the editing I am trying to achieve an overlaid video effect so that it looks like their is more than one person in the video. I also want this section to be edited to the beat, I am finding this section difficult because their is so many effects that are on each video then they have to be put together and it's making the video glitch and is not working properly yet. I have tried to re-insert the videos back in but the same problem is occurring. As you can see in the screenshot above this is the section of video that it glitching i have rendered it many of times and in the end video their will be more than just the 3 videos overlaying in this section. So hopefully i can resolve this problem and carry on editing so that all the videos are working.