bk85 Although quite off topic. I think they are Ion-exchange, you might find more information on their website:
You’re talking about a scale problem even though you’re using filters so I don’t really understand why you think it’s off topic to actually understand how the filters work. Both the BWT and in tank filters work in the same way - ion exchange.
This goes some way to reducing hardness and, depending on how hard the water is to begin with, can reduce it to very low levels. Unfortunately, it does nothing to change alkalinity. With very high alkalinity you’ll still get scale even with low hardness. That you aren’t seeing scale when you boil the water isn’t particularly relevant as your machine operates at temperatures above boiling point. At 100c, with 40mg/l alkalinity, you’ll only see scale forming if hardness is over 134mg/l. The problem remains that when heated to very high temperatures, the filtered water will deposit scale if there is hardness and alkalinity present e.g at 160c, if alkalinity is 40mg/l from carbonate sources then you’ll see scale forming with hardness above 15mg/l, an ion exchange filter will likely not reduce hardness below this point, and alkalinity will probably be higher than 40mg/l so you have an even lower tolerance. To put it simply, you are seeing scale form in the service boiler either because your filtration is not good enough, or because you aren’t draining the service boiler regularly enough to refresh the water and flush out the concentrated minerals in there…..or it could very easily be a combination of those things.
With regards to getting the machine repaired under warranty, sorry to say I don’t think you stand a chance. It may not need a repair, could just need to be descaled. But if it does, and damage is a result of scale build-up (or running a machine that is leaking as a result), that is not something the manufacturer can control so they aren’t at fault.
EDIT: Oh, I see you’re focusing on the compression tube and the steam. Well, the scale build-up still applies. However, I don’t see any corrosion aside from tarnishing to numbering on a bolt. Certainly, nothing that warrants repair. I can’t remember exactly but I think the brownish mark you see close to the hose on the boiler is flux from welding or something along those lines. Difficult to really see from the picture but it’s unlikely to be rust. Could also be burned on residue from the water after it has evaporated.