Stripped out rear fender holes?

I bought a rear backrest from Star Accessories (non quick release) and have taken it off and on maybe only 6 times. I took it off one last time and when I went to put the stock bolts back in I was not able to screw one back in all of the way. Kind of like the threads werent there. I am guessing that the screw holes were a soft metal and got jacked up from switching bolts. Anybody have this issue or know how to fix it?