LP Fireplace glass Blowing out of door

I have a Monessen 320DV4136NV (without blower) natural gas fireplace that was installed while my house was being built in 2001. The glass has blown out of it 3 times (the last time being last night). We are empty nesters so there is not activity in ther home that would scratch or damage the glass. There has not been any cleaners containing any abrasives which could scratch the glass. The 1st time Monessen replaced the entire door. The second and third replacements were done by different fireplace dealerships. The last replacement was not even a year ago, The glass didn't even have a chance to get dirty! No one (includung Monessen can tell me why this is happening. The door does have the optional brass door trim from Monessen. CAN ANYONE HELP ME! Outside of the shear expense, it's dangerious to have bits of glass being expelled into our living room.
Sinceredly,
Frustrated by watching TV in goggles
Dean C. Sippel
Sippeld@Patrickind.com