Direct Offline Processing (DOP) Doesn't Work On Certain Events

Just upgraded to Nuendo 8 from 7 and I’m still getting used to this DOP workflow. It’s great when it works, but today I’ve run into a huge blocker where DOP keeps throwing up exclamation points in the status column of the process list area of the DOP window. I’ve included a screencap of the bug/error. I can’t seem to find anything in the documentation about what the exclamation marks mean, but it’s clearly not processing the event. It’s only on some events. I’ve tried switching between mono and stereo tracks, as well as mono and stereo plug-ins, but no dice. Anyone have any idea what’s going on here?