Hi Theo,
For testing openwrt firmware on the MVixBox (same hardware), I had to break the case to get to the serial port.
Only way to hold the box together after that was with some strong adhesive tape.
You can hold the trays in place using adhesive tape or with a rubber wedge to the frame.
It just requires a bit of DIY.
These NAS boxes are quite old now - but still used by many.
Best hope is that someone has one lying around unused.
Hi Aquar;
The tape solution will do for the time being. But I hope that someone can help me with spare part, from an unused one

Thanks for responding!