Front Window failure Bailey Ranger

We bought our 1st caravan this Feb (2008 Bailey Ranger 510/4) after being away for 2 weeks put the van back into storage after thorough clean at home. 1 week later - Monday - I went to the van and the front window has a 6 inch vertical crack on the outside of the front window and directly behind it a 8 inch crack on the inner pane. Both cracks start at the top there is no external damage - chips etc and the crack start slap bang in the middle of the screen at the top, there is also no deformation of the top hinge - so nothing trapped underneath.

My supplier - are trying to tell me the cause could be due to the current temperature fluctuation that we have had over the past week? and caused the window to flex. This seems very strange to me but being completely new to caravaning I don't know if this possible.

Any help suggestion?

Yes the Ranger is the one with the large single front window - I am dreading the estimate