the warranty might exclude damage caused by things like "any misuse or unauthorised alterations". In which case the onus would likely be on the manufacturer to prove that "misuse or unauthorised alterations" had occurred (not the other way around
Well yes, but you’re missing a massive part here, and the key part, which is the damage could have occured due to wear and tear, it is not a case it’s either faulty or it’s misuse/unauthorised alterations. There is a massive area of wear and tear in between.
The manufacturer can just say it’s wear and tear and walk away. Whoever litigates has the onus of proof. The manufacturer isn’t going to take her to court, there is nothing for them to do so over, they have denied her claim, so for them it’s over.
If she then decides to pursue it, she then needs to prove it was faulty and they were liable under the warranty. She can’t do this. As they are the defendant, they don’t need to prove anything, she would need to take her case to court with the evidence it’s faulty. If she does this then the onus of proof is on them to defend that.
That’s why they are called claimants and defendants. She needs to claim it’s faulty, and provide evidence, they then defend against it.
She’s stuck because she actually doesn’t even know if it was faulty never mind Provide evidence.
Your answer is erroneous because it assumes if it’s not misuse, then they are liable, this is not the case, if it’s wear and tear, she’s liable, not them.