Garage door opens itself?

I close my garage door and it opens right back up again. During his visit, he mentioned speed spindle has been a factor causing the motor to react. He adjusted spindles for "decrease" and "increase". It worked out fine. Door closed and I paid $70 for his 10min. visit. 48 hours later, I'm having a same issue. I called the tech again and he told me I'd need to swap the motor, and will give me $70 off to make it $429 + tax. Am I getting scammed here or should I contact other service tech?