Repairs z225 John Deere Tensioner Spring for Transmission Drive Belt

Hi. First time here, hope I do this correctly. We have a 2011 z225 John Deere mower. It has about 521 hours on it. Two weeks ago, the tensioner spring broke. I went to our local John Deere. They ordered part #M170332 and it was the incorrect spring. Then they ordered part #M72291 and it appeared to be the correct part. We put the spring on and I cut for about 1 hour and the spring broke again. Could they have ordered the wrong part again? Could it have been a defected part? Do I have other issues, causing the spring to break? Any assistance appreciated.

Post a picture of the spring.
Never heard of this happening before
Usually the spring flogs out the mounting hole.
Check that the tensioning arm moves freely.
It requires greasing at regular intervals.