Leaf Blowers

I 2 bought EB7001 part number 57416101 short block from Jacks small engines on 2/12/13 put them on 5/12/13 first one had no problem second one muffler bolts came out then try to put back they will not stay tight and keep coming on the threads in cylinder are no good.i did not over tight them i did loots of these machines and never had this problem this is first time. So i thing the threads were messed up i did not force it in they went smooth.So i hope they will place the short block or send me a new cylinder and rings i fix it myself. Jacks small engine said they will not cover cause redmax will not.