Plasma 42 inch goodmans tv. i have just have my tv repaired a week ago and the picture gone again

Question

i have just have my tv repaired a week ago and the picture gone again i was charged £290 for the lower drive pcb 6871qdh0678 to be changed and ysus pcb 6871qyk029a. now they are saying another part on the pcb board has blown and needs £138 to fix surely they should have found what caused the fault the first time? somthing must be causing these to blow,