Let me introduce myself, JP McNabb Lic#523892 and doing almost any kind of overhead and sliding doors for the past 30 years. We have a no charge if we can't fix it policy.
The garage door is the largest moving object in your home. Therefore it must be maintained on a regular basis. One analogy I use is a car and you have to maintain that as well. Without knowing the specifics of the opener it is hard to guess what is going on and customer service should have explained that to the customer.
Here is what I would do on a service call, See how bad the stress fracture was and brace with a strut if needed. Check the outlet for power. Pre 1993 openers we don't work on due to liability issues, the openers must have two safety reversing systems. One the motor speed sensor, and second an IR sensor mounted 6 to 12 inches from the floor UL325. Then lube the door and opener then test the door by hand, then by by opener, there again depending on the UL standards.
There are a few bad apples out there so call at least three on any job around the house and trust you instincts.
JP McNabb
www.sosdoor.com
CA