another sync problem

I've got 2 DL2s in a 1X2 collage. I uploaded a custom graphic that is just some bold text...white on black. Then I put the graphic in a Shake n Bake effect. After a while I'm seeing the fixtures get out of sync, causing the text to split from the collage mode. I've messed with the sync to and sync type, but this isn't a video clip, it's a jpeg. The only movement is from the Shake n Bake effect. I ended up resetting the fixtures, and now they are synced again. I guess I don't fully understand the sync options. "Sync to" is to assign a graphic layer a device ID to sync up with? Is this the ID I gave it using the CMA? "Sync type" is what? For this, do I put "sync type" to the graphic layer I'm using? I think I tried all this, but got no results.