+1 It's not worth it. Don't use it. At this point assume it's a faulty cell, but I'd watch the charger to see if you get any other anomolies.
i really wouldn't even experiment with it any more. these things can cause real damage and its just not worth the risk.
I got the message 
Tomorrow morning I am disposing it. Thank you all! 
Personally, I might remove the protection board and test the underlying cell voltage if it's getting inconsistent readings.. But then I would not recommend doing anything with it, as if it was a genuine reading then that cell could potentially be one that will put you off li-ion forever, possibly through costing you a few fingers.