Issue with Rose Bikes refusing to honour bike warranty

Has anyone ever had an issue with a bike manufacturer who has failed (or refused) to honour the warranty?

I am having huge problems with Rose Bikes (Germany) at the moment.

Recently, I had an incident with my bike (ROSE X-LITE TWO Force, 2.5 years old). There was no crash. The bike was not involved in any impact or accident. Just a freak incident.

I was just beginning a climb and after perhaps the second pedal stroke, I just felt the pedals go slack. When I stopped to look, I saw that the eyelet (on the right side) where the axle goes through had completely broke. The force exerted from the effort on the pedals must have also caused the derailleur to snap. Such a freak thing to happen.

They asked me to send the bike to Germany for them to review, which is where the bike is now.

Rose Bikes completely rejects my explanation of what happened and tell me that I have to pay almost 1700 euros for the repairs (which includes a half price bike frame). They say that they believe I had fall with the bike - but this is complete bollocks. The bike has never been involved in any accident recently nor in the past.

My opinion is that the frame should be covered under the warranty.
https://www.rosebikes.com/faq/garantie
I also believe that they should cover the cost of the broken derailleur since this happened as a result of the frame snapping.

I have explained this to them several times, but they are sticking to their opinion that the bike has had a crash. They even showed me additional photos of scratches to the bike (on the brake levers, handlebar plugs and tops of brake hoods), but this is purely cosmetic damage that has happened over years of use (i.e. propping the bike against walls, or turning the bike over to do maintenance in the absence of a bike stand) - Just normal scuffs that you would see on any bike!

They even said that ifI wanted to get the opinion of an expert to review their findings, it would cost an additional 1500 euros! Ridiculous.

So now my broken bike is in Germany with them. They want 1700 euros for the repair (I only paid 2200 for the complete bike 2.5 years ago!). I am completely at my Witts end with them.

What can I do from here?

I have attached photos of the damage to the frame and the derailleur, plus the photos that Rose Bikes sent back to me of the (cosmetic) damage to the hoods.

Any advice is greatly appreciated.