Cracked glass in door of woodstove

Hi everyone, was after more sage advice regarding cracked glass in the door of my woodstove.

I’ve had a Jindara Duo for about 9 years and a few days ago the glass in one of the doors cracked. About 4 inches below top, horizontally. I'll try for a pic later. I’ve been all over the net and the usual reasons given like a log rolling / settling against the glass, over-firing, knocking it with something eg a poker, or over-tightening of gasket and glass seal bits don’t make sense:

• I’m careful loading splits and nothing settled or rolled, either that night or any other night in the past. I cut my splits at 600mm length and load them north-south ie door to door and there is a good few inch gap on both ends ie between split & door. If they do settle they can only roll sideways they don’t shuffle along their length towards the glass.
  
• I load the stove 95% of the time and never close the door on a split eg to force it in, my wife doesn't either (she's good at following those kinds of instructions. Portions at meal times not so . . . )
  
• It was only 10 minutes after starting so it wasn’t up to normal operating temperature let alone over firing.
• I don’t over fire anyway – only burn aussie hardwood well seasoned and with the blower on #2 and air grate closed. Have run the fire at standard temperatures for 9 years.
• No-one touched the glass with anything eg poker, split of wood when loading etc either that night or ever.
  
• As for possible over tightening of gasket seal bits, well I haven’t touched the gasket seal for 3 years, and we burn for over 100 days each year, so it seems ridiculous that that could be the explanation – unless gasket seals / glass pane bits tighten over time and should be periodically loosened? That doesn’t make sense to me.

Any thoughts on why it cracked? Anything I can look for to determine the cause? Any advice on how to prevent it in future, other than those things I outlined above and follow diligently already?

Thanks in advance!