These are all just temporary fixes. Usually this is caused by over-tightening the screws. Replace the plastic and just watch how much torque you use on the screws.
One method I use is when I use a driver I do not hold it with my whole hand.
I hold it with my thumb and 1-3 fingers. The less fingers you use the less torque you will use. Normally, I use my thumb and two fingers. Also, if you are using a power driver it can heat the plastic.