Seatbelt Pretensioner Explodes in Mercedes Vito

Hello fellow DIY enthusiasts.
Here's what happened to a 1996 Vito owned by a good friend: Both seatbelt pretensioners activated without any external influence. Thankfully, the airbags did not deploy. This occurred without any external factors, such as potholes or impacts. One of the pretensioners activated while the vehicle was moving (which almost led to an accident due to the shock), and the other shortly after when the ignition was turned on. The latter caused significant abrasions on the passenger's neck, which were not seriously harmful but still unpleasant. There has been no tampering or modification to the Vito's electrical system; everything is original and untouched. Subsequently, the airbag warning light came on. We have now removed the airbag fuse to prevent a potential explosion of the airbags.
Given that this situation is absolutely dangerous and unacceptable, the question now is what we should do. My plan is to go directly to the Mercedes dealership and explain the issue. I will mention that I intend to report this incident to a higher authority within DaimlerChrysler, and possibly also to organizations like ADAC or even the press. Then, they can figure out how to address it properly.
If anyone has a contact address at the Department of Commerce (DC) that one can use in such cases, I would be grateful. Or if someone has a better suggestion...
I know this isn't particularly related to specific vehicle technology, but I hope no one minds. Oh, and unfortunately, I don't have diagnostic capabilities for Mercedes; like many here, I'm focused on VAGCOM.
'Best regards from a fellow enthusiast,' or 'Greetings from a car enthusiast.'

Try to find out if there have been any recalls for this model. Sometimes, people are not even notified when a recall occurs, which happens relatively often with older cars and/or models with fewer features.

It will probably be enough to just visit the next Mercedes dealership. This should be done free of charge for the customer, as it's likely embarrassing for the manufacturer. If they give you trouble, simply threaten to report them to 'Autoblöd.'

Something like that shouldn't happen, as it could lead to a fatal accident.

Unfortunately, something similar also happened once on a Passat 3B/BG with the side airbag. Again, without any external influence.

Can you rule out water ingress? Any bodywork modifications? New windshield/window(s)?