I'm a big believer that the unexplained front windshield cracks are caused by frame twisting. A few years ago, before I purchased our coach during my research phase, I came across a beaver related blog (maybe even on here) explaining the reasons between 4-point and 3-point jack systems. I couldn't believe it was simply a cost saving measure, in fact it was more of an engineering solution to negate windshield cracking by allowing the front frame to pivot from side to side while the rear jacks leveled the coach.
A lot of this has to do with the operator's procedures while transferring from on the road operation to parked and level. purging the air bags (as normally should be done) will allow the chassis to drop to the frame of the axles, and if the ground is slightly uneven, those axles could be counter inclined to one another causing some minor frame twisting as it settles down.
Now I proved all of this to myself recently while doing a 12 hour rest stop layover. I didn't want to go full level set up, so I purged the air bags by about 50% and only "touchdown" the front jack (not lifting the coach as I was rear high) and then dropped the rear jacks and leveled. We heard a pop, didn't know what it was until next morning we saw the crack in the windshield. I believe I purged the air bags farther than I had thought dropping the chassis near bottom to the axles, didn't raise the front end off the axles high enough to provide "wiggle room" between the axles and the chassis (and I usually raise approximately 4 to 5 inches above not just "touchdown") and we paid the price.
Now, no matter what: The front jack goes down. Lifts the coach by 4 or more inches and then I level with rear.
My current procedure is to turn off the engine, Purge the air bags, deploy the slides, drop the front center and raise front end, then drop and level the rear, and adjust side to side, and finally front to rear (never lowering the front center jack).
I would make the argument that if you have a 4-point jack system, that the owner should drop the front two jacks down to "touchdown" (maybe even all 4) purge the air bags, deploy the slides, and then level the coach. This would at least keep the chassis above, and prevent it from touching the axles. But I would run that past BCS first as it may effect the slide deployment. Right now, from what my manual says, I should purge the air bags then deploy the slides to prevent jamming it with a (possibly) twisted frame. Then level.
But, for instance, if you purge your tanks and your front passenger wheel is high, front drivers side low, and rear passenger side is low, and rear drivers side High due to ground level, then your frame is twisted anyway in some cases. I would tend to think that the coach frame is most level (stress free) when the air bags are at ride height. Thus -to me- touching down the jacks then purging would make more sense. And you know what? I may choose to modify my procedure to touchdown the front jack then purge in the future, but my current procedure has been successful with the exception of my small stOopId shortcut at the rest stop that one time. I know what I did caused the crack -even when my copilot questioned me, I did it anyway. Lesson learned.