2005 Highlander cloth seats moving

The drivers seat is again loose on the left rail with slight movement that can startle me during braking. This vehicle has been in at 6 times for seat problems - most not fixed the first time (not counted) - now the service manager says "it's normal" "not a safety issue" "I would pass it for inspection" and other baloney. Does anyone else's seat shift? Didn't do it new and I betcha I could comb car lots and not find any that shift. I have the extended warranty...