Whole video turns whiter when there is a lower third or overlay playing

I created a simple lower third with my twitter and then I saved it as quicktime with alpha channel to reuse it.

The original animation plays well at the beginning of the video. The problem is at the end. I added the quicktime overlay and another animation for youtube subscription. In the rendered video when those animations are playing the whole video turns lighter.

Then I removed the quicktime twitter overlay and copy/pasted the original, but the effect is the same. The same lower third renders well at the beginning, and the copy at the end makes the vide goes lighter.

I tried using a mask to limit only the area where the overlays are visible, but issue persists. Also tried with Disolve blend mode and rendering in max quality.

This never happened to me before, although this video was a bit overexposed and therefore the effect could be more visible.

Is there any known issue about this and a way to solve it?