Hi!
We have the exact same problem in our PAL studio. We use a JVC KM2000 mixer. The Blackmagic card is connected to one of the mixer inputs, and receives the mixer’s blackburst as external reference. No matter how hard we tried, we couldn’t get the phase jittering to stop on the mixer output. We can easily sync up any other equipment with the mixer(cameras, DV players, etc), but the Blackmagic card gave us quite a challenge. Any ideas?