500C – Luggage compartment no longer works – Software error?

Our 500 convertible has repeatedly caused the following error: In the situation convertible roof open and driver door open: A click to open the trunk leads to a system error and the boot flap no longer to open. The first time the car was in the workshop and got a SW update. Now it has occurred again. Do you know a solution? Is the problem already very well known? What to do in sebst help? Thank you!!!