Were they the silk pins you are using on you DWR, or your 'normal' quilting pins?
Were you pulling the pins as you went, or sewing over them?
Were the pins that were found in the machine bent?
Do you have a single needle plate or the zigzag one?
If they were the thin pins, you sewed over them and they were bent, my thought is that the needle hit them & forced them into the machine. especially if you have a zigzag plate.