I don't know for sure that this is a Censusplus problem, but it seems consistent so far... basically, sometimes if I do a /who on someone while Censusplus is running, it won't pick up everyone who matches the text - this seems to only happen when I'm searching for people where there's less than 3 online at a time, but it's very hard to notice it's happening at all unless I'm specifically /who'ing someone who I know to be online at the time and wonder why it doesn't pick it up.
Example: earlier I did a /who on character named Dna who was talking in trade... Census was running, but did the interrupt as usual, but only result I got was some other character beginning with Dna (forget actual name). I repeated this a few times, then told Census to stop running, ran /who again, and this time it picked up both characters.
I've no idea how or why Census could be causing it, but it's not the first time I've seen it. I've only noticed it on searches where 3 or less characters match (ie it gets printed in chat window instead of in social pane), but that's not to say it doesn't happen the rest of the time, just that I've not noticed it then.