I'm doing some simple still pictures with transparent backgrounds and moving text over a video layer. The soft drop shadows on the layers are glitchy (both the text and the pix). The shadows have a jerky little change in size every few frames at random intervals. I'm working in DV resolution, 16-bit, and bringing the Motion project into Final Cut for render. Any tips on what might be causing the shadow glitches? Thanks.
Final Cut Studio 2, FCP 6.0.2, Mac OS-X 10.4.11, Quicktime 7.4, After Effects 6.5 Pro, G5 Quad 2.5, Kona-LHe V5.1, 4.5GB RAM, Nvidia GeForce 7800-GT 256MB, G-RAID 2x1TB FW800, 6TB RAID-5 (Enhance E8-ML, Highpoint 2322), Panasonic HVX-200P P2.
This is an old post, so I'm not sure if you're still interested in the answer, but I've been dealing with similar problems and have read that other people have had problem with drop shadows in Motion also. In my project, they caused the associated images to oscillate, jumping around and warping in size--especially when I tried to include a video file in the layers.
My work-around was to manually create the drop shadows with a blurred shape layer. But you could always do it in Photoshop or Illustrator, or Gimp if you don't have those.
Even if this doesn't help you out, hopefully it will save someone else from wasting the time I did trying to figure this one out.
There are few issues with Motion that is for sure. It is buggy and not very stable, I hope Apple continues to work on improving the stability of the app. maybe in the next version of Apple Motion. However, here is a link to a free filter that I use often to produce drop shadows.