Solid-Rocket Motor - Concerns About O-Rings. Pg 1

Further investigating their concerns about the Solid-Rocket-Motor joints and the potential failure of O-rings, NASA officials met with outside experts and representatives from the company supplying the O-rings. 

Following a review of the evidence, "their [the supplier's] first thought was that the O-ring was being asked to perform beyond its intended design and that a different type of seal should be considered."

This is the first page of the memo which documents the visits.  Click on it to  expand the view.

Credits

NASA memo online, courtesy NASA.