Do you have locking bars on your slide? If you have maybe one is binding as it unfolds causing slide to lift on one side. The slide does lift as it starts in but your rollers should be on the floor at this point if you can watch it as it comes down near floor as it lifts press button again and slide will stop at that point.
Check locking bars to see if they are free and check under the slide you may have a roller off roller braket or something under slide room.