My machine has also arrived, and I can see this being a problem eventually. Either by incorrectly assembling the bungee cable (this is how the retention mechanism is referred to in the documentation) or by the loosening / stretching of the cable over time. The latter can be fixed by replacing it. It is also possible to build a guide around the belt from cardboard or plastic, if one is a DIYer.
Also, why the downvote, potential buyers of a thousand plus Franc product are not interested if it has an inherent design flaw?!