Mask under 2 clips with desolve between fails during disolve

I have a png file with an alpha cutout in it I'm using as a mask. The mask is under multiple clips. The clips have dissolves between them but the mask fails only during dissolves. I've tried making a compound clip out of the clips but mask fails differently this time.
Ideas?

Semi solved.
So I tried making the clips with transitions between them into a Compound Clip many times. Worked better than without the clips in a CC. Still, under the mask the clips show fine but where the transitions were, there was an edge of black just inside the mask. Although without the clips in a CC, you could see the entire masks black part, which covered the screen other than where the clips shown through, but only during the transitions. I solved this by once again making a CC of the clips with transitions in the Timeline and to get around the black edge that showed up during the transitions, I bumped up the scale of the CC under the mask, which in turn grew the black edge up under the mask also. Kind of a workaround. Fortunately the scaling up of the CC didn't effect the overall edit but man, I spent hours on this yesterday.

P.S.
I also did a "Render in place" on another set of clips with transitions between them, on top of the same mask. Same issue here but same workaround. Upped the scale of the rendered clips.