I just replaced the liner on my 20x40 IG pool and would like to know which robotic cleaner will be the safest for use on the liner. I have a Blue Pearl that has worked well for about five years. I need new belts from the motor to the drive section and the filter bag could probably use replacing. Before I spend the money on parts I want to know if there is something better out there. While I cannot prove it I believe the unit wore down the liner near the water surface as the pattern was very faded there and where the walls met the floor. Is there something that will be more gentle on the liner?