I'm aware of this issue. The fix which
MPC-HC used to support animated (fade-in/fade-out transparency) VOBSUB doesn't function with xy-VSFilter. The current behavior is a workaround to at least allow something to be shown rather than nothing (like VSFilter 2.39), but I'm unsure how to fix this properly without our developer around. I suspect somewhere in the queue or render code he is making assumptions that bitmap subtitles like VOBSUB would never be animated.