If your Betta is moving in circles, the issue is usually caused by either a faulty propeller or a front ultrasonic sensor problem.
Check the Propellers: when the unit is turned off, each propeller should spin freely with just your finger. Inspect the propeller shafts for any debris, hair, or string wrapped around them, as this can cause uneven movement.
Clean the Front Sensors: Betta uses front ultrasonic sensors to detect walls, slow down, and redirect itself. The unit also reverses every few minutes as part of its built-in navigation algorithm (since Betta does not have pool-mapping capabilities). Try gently wiping the front sensor lenses with a soft microfiber cloth to remove any film or residue that may interfere with detection.
Check Motor Installation: If you recently installed new propeller motors, note that they are side-specific. Each motor has a marking near the set screw that indicates whether it should be installed on the left or right side when looking at the unit from the back. Incorrect placement can cause circular movement.