U600 fragile screen or lcd
 

Except all flex cable and LCD unit problems in U600, recently I had a tide of phones coming with screen lens damage and damaged LCD's. 2 of them came back to me with the cracked LCDs, 2 weeks after the LCD unit was changed. I do not see crack on upper glass, the crack must be on the lower glass.
What should i do to avoid such damage? Change the facia? Or buy better LCD units?