Spec-Savers blind for an inferior product...!

We are clients of Spec Savers for many years. My wife had her eyes tested in June/July 2019. She made a choice of the frame as advised by the technician and received her spectacles a few weeks later. She only started using them in the September holidays. Within two months the one ear of the spectacles simply broke off. We took it in, they inspected it and replaced the complete frame. Three months later, early in January 2020, the same happened. Needless to say, we had to explain. How do you explain a ear which suddenly came off? She is wearing her specs every day, is a housewife and my artisan-assistant in the sense of travelling with me, fetching tools, doing the admin etc etc. Nothing physical that can cause the spectacles excessive wear or the ear to break off. As a matter of fact, she is again using her five year old spectacles, with which she never had any problems. Furthermore, in January the assistant at Spec Savers declared the frame as a factory fault, and he even made a written note of it on a copy of the original invoice at the time. We came to an agreement that, should the frame break again, Spec Savers will claim it from the insurance. Now, six weeks later, the replacement frame, same type, design, model, whatever it is called, breaks again. The ear, followed by the test, just drops off on her lap as we were driving in my vehicle . Of cause I am annoyed. And when I approached them, it suddenly is not a factory fault anymore. Upon hearing she is my assistant, she suddenly "climbs into roofs, going underground..."! (My wife happens to be in her late fifties....!!!) Then she was accused of taking the spectacles off in an incorrect way. So I asked him for the manual on how to take your spectacles off. The lesson in it must be that everything in life that breaks is because you are not using it correctly. you need to pour the water into your kettle in a correct way, hold your steering wheel in a certain way, etc etc. What a laugh. Their suggested solution is that they will claim the spectacles from their insurance, but I must pay the excess amount, which is dependent on the price of a new (stronger) frame. We do not have a problem taking responsibility for mistakes we make. But I am positive it is not her mistake. As a matter of fact, I am willing to have the specs tested at an appropriate institution. If the outcome is that the specs quality is above suspicion, I will carry all costs. If it is of inferior quality, Spec Savers pay all costs and replace the spectacles and all costs involved. My problem is simply this: When she selected her frame, it was done with their advice. They knew what the lenses were gonna be like, and at the time, you as a client put your trust in them. Then, when the frame broke the first time, we thought it to be a once-off. The second time, we start to realise it is a poor product. As I said, it was inspected by Spec Savers and declared a factory fault upon manufacturing. They do not have another frame for the lenses, so the lenses will also have to be replaced, making it very costly. Thus the insurance claim option. My questions is this: Is it fair to charge insurance for this poorly manufactured product? Secondly, is it fair to expect I must pay the excess amount on a poorly manufactured product? It is not so much the money, but the principles. Like I am buying a car with a faulty engine, and when the dealership mechanics cannot fix the fault, I and the insurance company must take responsibility, pay the excess and have the car replaced. Please explain it to me, Spec Savers. Or take me up on my challenge.