lol - the dreaded "tensioner" is a
potential threat if not installed correctly or maintained, I suspect ya did both
It could dive into the spokes and destroy the wheel which I'm sure you've figured out by lookin' at it - it's a shame really cause it would be a simple matter to supply one that spans both bars.
The concern is for the many first-time builders that may foolishly think that all of the parts in the box will do the job they're supposed to do if they just bolt 'em on lol It's also about the only part that so easily endangers the whole build and the rider for the sake of tightening a bolt
http://motorbicycling.com/f11/chain-tensioner-suggestions-11815.html