Export from Adobe Animate to Media Encoder is causing frames to completely disappear

I'm an animation major and I've been working on my Intro to Animation Final for about a month now, and it's due this coming Thursday. I was about to finish my project when I suddenly encountered a problem. I export the file to media encoder from export video/movie occasionally just to see if everything looks and runs smoothly since my laptop lags sometimes when I play it in Adobe Animation. Upon exporting it, I noticed some issues with the video. Some frames were being covered up and others were appearing in front of layers that I know they should be behind. So I went back to look at my timeline and nothing was wrong at all. I thought that maybe I had too many layers so I merged some on the layers that were messed up. I exported it again and the sections that had issues were fixed but the parts that have disappeared/covered up by the background haven't changed. So I went to merge those layers as well, but nothing changed. I have no idea as to what to do.

I've attached the video below in case anyone needs to see what I'm talking about. Towards the end of the video, right after the dinosaur is electrocuted, there should be a scene of the main character breathing heavily and then the dinosaur falling over. But instead, they aren't there at all. I really hope someone can help since I am stressing out now.