Keyframing adjustment layer opacity causes cross dissolve to freeze the frame beneath it and fade to black

When using an adjustment layer placed above a piece of footage, changing the layer’s opacity with keyframes causes any cross dissolve transitions applied to the layer to both display a freeze-frame of footage beneath it, and dip to black (not in the normal “dip to black way”, but just fading from the freeze-frame to blackness).

The keyframes do not have to overlap with the transition, nor do they have to even be visible in the portion of the layer to which you applied the transition.