You're not joking Biff, the makers give a 2 day estimate for their trained techs to strip out the guts & replace case! (not cheap either!!) We just find it too much coincidence to have same cracking on so many units, the users are not 'That' careless, hence the search to see if problem is wider spread.
Note: cracks are specifically at top of rear case near fan recess, I tried uploading piccies but failed miserably.
Thank you for yor response though, nice to know someone out there's taken time to look & check.