AlV 69 Dodge GTS project

I noticed when I dyed my seat belts that the boiling water warped the plastic housings around the retractable belts to the point that they would not function properly. How did you avoid this dreaded fate? I assumed I must have let the belts stew too long.
Well the only thing I did different was not bring the water to a boil for too long. Once I go the water to Boil I turned down the heat pretty much stewed the belts lol
Total cook time was 40 minutes.