visual glitch on duplicated clip after rendering

[Lilly5D87]

I rendered an edit that I made that had one precomposed layer of all of my editing clips and one duplicated layer of the original precomposed one because the audio looped. There were no issues with the video until i rendered it where it got way less smooth and got theres very noticable visual glitches. I am going to attach a video of the glitch so hopefully that video is available to watch. 

[Lilly5D87]

oh i should also add i use after effects 2021, i have a macbook air 2017 and I use adobe media encoder to render my videos 

[Rick Gerard · Accepted solution]

I am guessing that your original source footage was an MP4 and it may have been a variable frame rate video from a mobile device. The other possibility is that you have fiddled with the render settings. 

The fix probably involves rendering a good DI (digital intermediate) from the original footage using a suitable visually lossless MOV or AVI format, then replacing the footage in the project with a proper production format.