How Do I Increase The Up And Down Force Manually?

I installed the 8165 Liftmaster operator for a customer in January. The operator had worked fine for 7 months. Then the door stopped half way up without my customer realizing it. She nearly drove through her door backing out of garage. The door springs and function were perfectly balanced. There was no unusual friction in the system. She says that this occurs about once in 20 operations. I do not want either Chamberlain or my company, Allison Door, to be sued for this very unsafe and unreliable operator. I have installed 2265, 3265, and 3255 operators over the last 12-15 years. I've been very pleased with them. I have only had one warranty call in nearly 1,000 operators I have personally installed. I have boasted about this incredible record of performance to all of my customers and to many others in the garage door field. With this new "travel module", where I have no control over potential premature stoppage, is completely unacceptable. If I cannot override this auto setting I will have no confidence in this technology "upgrade". I will be forced to look for another operator. I am extremely disappointed that you would discontinue the 3255 and believe that Chamberlain will regret this decision soon.