damn. :\
This is a token/accountant gesture and stern know's it.
They've done the sums and seen how much it is going to cost to fix that issue and are closing the books on your case.
Any physical replacements or service that they have to do will reduce profit margin on the machine by a non trivial amount.
What they should be doing is taking the entire machine back and give you a new one (has this ever happened?).
With the old one they could recover parts and remake with a new playfield and mark it as refurbished like they do in other industries. It's not dishonest and the new customer knows what they are getting at a reduced price.
Hell, don't even do anything to it and mark it down with the known quality issues. Plenty of route operators might take a cheap version like this!
All of this makes me SUPER wary of ordering something new. I discussed this with my local distributor after I had a deposit in for a jple and the best I could get was a "we'll look after you". When asked how this sort of thing would be resolved it was "it depends on stern", so I cancelled my order. and got a refund. As much as the distributor wants to fight for me I could see that it wouldnt help.