I have found that if your racquet head gets deformed during stringing, its usually the fault of the stringer. Probably and this is from personal experience, the racquet is not seated properly. You will find this usually from a stringing machine that has 6 pts of contacts instead of the 6: 12: oclock contacts.
Need to seat the racquet very loosely in the bed so that the contact pts of the machine just barely touch the frame.
Strange but its what works.. there is a good video from babolat, you can search on the internet on how to properly seat your racquet. It specifies for babolat machines but I"m sure its universal for any 6 pt mounting systems.