Many thanks for your feedback!
I guess it would have been « simpler » if it was related to the roller bridge. I was aware of this problem and asked my luthier to check the roller bridge, and he told me he would inspect the whole instrument. But when he saw the guitar, at first sight, he told me that the neck was not properly set up. When he gave me back the guitar, he explained to me that the neck, whatever he did, always got the wrong curvature, and he could not loosen the truss rod any further and advise me to report this to my dealer. So my dealer wanted to check the instrument by themselves to confirm this. They also told me that if it was only a problem with the roller bridge, they could swap it for a standard bridge, but they had to do it themselves because of the warranty. When they received the guitar, they told me they have to send it to a Rickenbacker specialist to confirm the problem. After a few days, they told me the instrument could not be fixed. I suppose I can only trust all these people.
I guess my 325 will not be underneath the Christmas tree.