Two things to try (in the order as given):
(1)
(rightclick >) Options >Preferences > Video > [Video rendering]
Select a different rendering mode.
(What is presently selected?)
(2)
(Rightclick >) Options > Preferences > Frame and thumbnail capture
Maybe try a different setting of "Convert captured images in software"
(Both YV12 and YUY2 selected?)
(What is your Graphics card?)