The German ride manufacturer of the Texas Giant said blame rests with Six Flags for the death of a woman last summer.
Six Flags recently said in a court filing the cars riders sit in on the Texas Giant were defective. The park joined a suit against Gerstlauer Amusement Rides that was filed by the family of the woman killed.
Rosa Esparza, 52, fell 75 feet after being ejected from her seat and died in July 2013 riding the coaster. Esparza's family is also suing Six Flags in addition to Gerstlauer.
Gerstlauer said in its filing that Six Flags opted not to put seat belts on the Texas Giant, a decision that dated back to 2011.
The ride maker also said Six Flags failed to use the "test seat" given to them. Gerstlauer said the test seat had a "red light indicating that a passenger's size was inappropriate for the restraint system."
Gerstlauer also blames Six Flags for poor hiring and training of the ride's operators and their failure to properly perform a "push-pull" test on the ride's lap bar.
Gerstlauer wants a judge to dismiss Six Flags' suit against them. There is no timetable on an action from the judge.