Hey
@Stefan Mikes --understandable. In any of these cases, I don't believe it should be seen as "blame," more so path of resolution. Because Bosch makes the system, we cannot control the bike. Because ______ makes the eBike, they cannot control the system. What we can do really well at Bosch is study and know how our OEM partners are incorporating our systems to their eBikes. When we learn of an OEM using let's say lights made by a third party company (since Bosch does not make lights), we try and have that info so if something comes up we can help steer the dealer in the right direction, or the consumer in this case on a forum.
Trek's speed sensor is one instance of an OEM making their own part within the Bosch system. The info here is to steer the rider in the right direction of dealers. For even more transparency, I carry a couple of these sensors around in my van if I ever come across a dealer who may not have a Trek account but is servicing a customer's bike with this part. That's how we interpret service!
Hope that helps.
Cheers!