This mostly applies to Late Answers and First Posts, where it's relatively common to see the same post in both. The individual behaviors seem to be:
If action is taken in one queue, when the same post comes up in the other queue "I'm Done" is enabled immediately, which seems sensible enough (what else am I going to do, flag it again?), though not showing the same post at all would arguably make more sense.
The "No Action Needed" button is mutually exclusive with taking an action (amazing!), and is disabled if you do something that would enable "I'm Done". Also sensible.
After flagging a post as a non-answer in one queue, when it came up in the other queue both buttons were enabled. If nothing else, I'd think the "No Action Needed" button should be disabled in this case.
I'm not sure how it's currently handled if "No Action Needed" is chosen the first time, since I'm more likely to either skip or take action on the sort of posts that show up in both queues. It doesn't make much sense to me to show a user the same post they've already declined to act on, though.
Seems a pretty minor bug, but figured I should mention it.