I managed to fix the error by just moving 1 layer, like i said i just had
1 - With some footage mp4 on it(No effects applied) in this layer i was using only the sound the video was hiden
2 - In this layer i had a precomposed layer in which i had another mp4 file cut in different parts to make a certain scene (No effects applied)
3 - Same layer duplicated and set on Overlay.
However i managed to fix it by just moving the layers i belive, i restarted AE a couple of times too..
Dave i'll keep that mind for next time. Thank you.
To anyone who still has this problem, there is an easy solve:
Use Control-Click to select all of the layers in the area of your composition that has the problem. So basically, the part that gives you the error when you try and render or play it.
Right click one of the selected layers and choose pre-compose. Just click OK and you will see that the layers have been minimized into one composition inside of your composition. It looks neater and it works with the rest of your comp. Notice that it does not change length, so everything is in sync/time as before.