Even if the regulator itself is not the problem, the recent repair made to your regulator most likely caused this plastic piece to break - which is why they fixed it for free. I love how they said that "technically" they are not responsible and make you feel like they are doing you a huge favor by fixing it for free. In my opinion they are 100% responsible. My guess is that they over torqued the bolt that secures the regulator to the window or somehow didn't align things properly before they tightened the bolt. It was probably the red bracket that broke. This is a small piece of plastic that costs 29 cents according to realoem.com.
I have to say, I don't like the way the did this repair. Gluing together a piece of plastic that costs 29 cents is not a good way to fix things. A few hot days and I can see this fix coming apart very easily. I am curious to see how long this holds together. Keep us posted. In the future, I wouldn't go back to that shop. They are wasting your time. If they fixed the regulator properly the first time, you wouldn't have had to take it back 34 days later. And now with their most recent repair, it looks like you are going to have to go back again in the near future.
This is why I encourage people to fix this themselves. I know most people don't have the time to do something like this or are not mechanically inclined, but sometimes it is worth it to take the time and do repairs like this yourself.