There was an issue with ppg glass windows on Bell mediums a little while ago, our fleet had three or 4 new ppg glass windshields crack, two cracked with the aircraft just sitting on the ground.
I believe it came down to a run of mis-formed windows, they were not contoured to match the airframe and when installed were put under constant stress.
I would check to see that the windshields fit properly when installing the next ones.