Hardware overlays

When I display a KinoAmp window with “Lock size to window” disabled and scroll within the window, the chroma becomes de-synchronized. It occurs when I scroll down for YV16 and when I scroll to the right for NV12.

I browsed the sources of both VideoOverlay and BMCVideo and found very few format dependent stuff which seems ok.
I suspect the issue might actually from the Dispmanx side.