I can't imagine your tensioner going bad after only 1 year. What happens when you turn the hollow 13mm bolt to relieve tension on the belt? Does the tensioner move downward and relieve tension? Does it move at all?
You may have stripped the threads on the pulley rod, creating the appearance that your tensioner has gone bad.
Also, just to check the obvious, does your current tensioner pulley have metal grooves or is it smooth? Since the back of the belt wraps around the tensioner pulley, the TP should have a flat, smooth