2006 WW FT Tiresvalve Problems

I BOUGHT A NEW 25' GOOSENECK FLATBED TRAILER BUILT BY A COMPANY IN TEXAS (LOCAL RETAILER CHANGED TRAILER NAME). I HAS ABOUT 10,000 MILES ON IT. IT CAME WITH 4 COOPER DISCOVER RADIAL AST TIRES ON IT. TWO OF THEM ARE STILL ORIGINAL. THE TIRES ARE NOT AT FAULT, THE VALVE STEMS ARE AT FAULT. WITHIN A 6 WEEK PERIOD, ALL FOUR VALVE STEMS CRACKED NEAR THE RIM AND DEFLATED THE TIRES. THE FIRST INCIDENT OCCURRED ON INTERSTATE ROADWAY CAUSING THE TIRE TO HAVE TO BE REPLACED AFTER RUNNING FLAT WHILE MAKING A SAFE STOP. SECOND TIRE (A FEW DAYS LATER), SAME THING. THIRD TIRE DEFLATED IN MY YARD, SITTING STILL. I SAW WHAT WAS HAPPENING WITH THE STEMS AND REPLACED THE FOURTH WITH THE THIRD, NO DAMAGE. COST ME $284 TO REPLACE TWO DAMAGED TIRES AND NEW VALVE STEMS AND $225 FOR ROADSIDE ASSISTANCE. $3 FOR TWO VALVE STEMS...