The start button of the CristalProfi external filter is stuck and does not return to the original position after is is pressed.
The most likely cause of this is the start button being pushed at a slight angle.
Solution: Please unscrew the 4 screws at the corners which secure the lateral handles. After the handles are lifted, you will see 4 more screws which secure the pump head cover. Unscrew these screws. Now you can lift the pump head cover.
This start button is screwed onto a connecting piece. Please turn the button to loosen it. The tension on the spring of the start button usually releases itself after the first rotation.
Replace the pump head cover and the handles in reverse order.