When the battery drains down to below 20% capacity the scooter will limit the top speed to preserve the remaining battery. If the scooter is limiting the top speed while the scooter has greater than 50% battery then the issue is likely with the controller or with menu settings that are governing the speed.
Please check out Changing the Speed Mode and How to Use the Levy’s LCD Display Console & Change Menu Settings to make sure all settings are adjusted properly.
If the top speeds are not being limited by settings and the scooter is still unable to reach expected speeds then there may be an issue with the firmware of the scooter's motor controller. If this is the case, the best course of action is to replace the motor controller as seen here: Swapping out the motor controller on the Levy / Levy Plus.