how do i fix my toyota celica gt handbreak?

since i replaced the parking brake shoes on my 1996 gt celica i have a problem. when i stop faceing uphill and apply the handbrake the pull is firm, but when i take my foot off the footbrake the car rolls back and there is two more clicks on the handbrake to hold it.this does not happen when faceing downhill ! i didnt notice this problem before and have tried a second set of shoes.