I use a Rawlings Ti, and had 2 welds break on a foul ball last month. I talked to Tony at Mask-It and he unfortunately said he couldn't weld it and that it would cost me upwards of $250 to repair it properly.
I figured I was out of luck, but talked to my brother who does some tig welding, and while not perfect he was able to fix the welds. There was some minor brown-blue contamination, which realistcally won't affect the strength of the mask significantly. And if the welds break again, well, I was out a $200 mask anyway before the repair.
I understand a professional shop not willing to take on a job like this - They don't want to attach their name to something if they're not 100% and cant do it without contamination. But, my brother is an engineer, not a welder - if he can do it this well on a first try, I'm sure it can be done even better in the future. I'm happy with the results- looks pretty good after buffing off the top layer.