DeLonghi 5400 fault Insert coffee grounds container

Hello!
We have a Delonghi Esam 5400 fully automatic coffee machine. We are having problems with the error message on the display that the coffee grounds container is not in the machine.
However, despite emptying the coffee grounds container, the error message does not go away. The interior was also only cleaned dry. The error message means that
the coffee grounds container is missing or has not been put back into the coffee machine after emptying.

I have read that the cause may be that something has become wet in the machine. However, moisture cannot be detected. The machine was only cleaned dry on the inside.
The error message disappeared after a few days. It can therefore be assumed that the cause is moisture that has dried out. However, it has not been possible to determine
what has become damp and
why it has become damp.

Does anyone have any tips or advice on how to solve the problem permanently?