Question Graphic Compositor not able to play two videos at once

As per title, I can't seem to be able to make two videos play at once in the graphic compositor: not if I put them as individual sub-layers in the same Composition Layer or if I make two individual Composition Layers (one for each).
Both video have alpha channel and they work with no problem at all if I compose one of them over a background static image, but I've been wrecking my brain for hours without being able to see both video layers play at the same time.

Any help would be much appreciated.