Does it still render an MOV file fine? How are you doing the rendering? Are you using AE's render queue or the Adobe Media Encoder?
This kind of looks like you are using puppet pin and you've fouled things up there. This happens when you apply puppet pin then you animate the layer or you move the layer or you have not properly set up puppet pin. You talked about rendering an MP4 but you show us a partial comp panel and there's no way to know if this is your rendered movie or if we are looking at the compassion you are trying to render.
A screenshot that doesn't show all of the modified properties of the layer you are having problems with and a workflow description that says nothing more than this isn't working does not give us much to go on. I'm almost sure that it is user error. Please include a screenshot if your timeline with the layer giving you problems revealed. Press the U key twice to show us all of the properties of that layer that are modified or have keyframes. If you don't want to show us all of the comp panel then blur out the parts that are sensitive. Then maybe we can help.
Oh no, I don't have any problems sharing the whole interface. I just didn't know it was necessary.
this is the video i'm trying to render. i used AE's render queue for the .mov, and afterwards i used adobe media encoder to render the .mp4.
But indeed, I used the puppet pin and it could be totally true I fouled things up. I only think it's kinda weird, because it happened after rendering the file into a .mp4 with adobe media encoder.
and for Szalam, it doesn't render the .mov correctly anymore because the file changed after i got a .mp4.
You moved the layer with the puppet pin applied. You cannot do that.
Puppet pin defines a mesh from the alpha chanel of the layer when you place the first pin. When you use puppet pin it is important to turn on the mesh so you can see what parts of the image it is covering. If you had a puppet like this and the expansion was wet too wide the mesh would cover the arms and the body so you could not move the arms independently.
Moving the arm gives you this:
Changing the mask expansion to 5 pixels fixes the problem completely:
If you scale or move the layer after you have applied a puppet pin the mesh will stay in it's original position and the effect will be broken.
Any decent tutorial on the use of puppet pin should have covered these basic rules for the workflow. The solution is to make your puppet move using only the puppet pins or make your puppet move, pre-compose moving all attributes to the new comp and then move the entire layer.
For further instruction on the use of the puppet pin type "puppet pin" in the search help field at the top right corner of After Effects and check out the community resources.
this was really helpful! thanks! i didn't get proper education from my teacher tho, so i didn't really know about this, i just did something. you were a great help and you solved my problem! thanks!