N key doesn't work as expected

If it is still under warranty and the problem is recurring then kick up a stink until they give you a new machine.

Just a note you don't have a Mac Pro 2017, you have a MacBook Pro 2017, different things, there is a forum for MacBook Pros, MacBook Pro see if anyone else is having a problem with their N's.

Be persistent and always polite, but point out that you don't expect to pay thousands of dollars/ pounds etc for a machine that suffers a hardware problem from the get go and after having been repaired once suffers the same fault again. And because of this reoccurrence of the initial fault your confidence in that particular machine has been dented, and only a new replacement will restore your faith in the Apple brand. Oh and talk to the manager. I hope you bought this through an Apple Retail Store.

Ask in the MacBook Pro forum to see if anybody has a similar experience with 'odd' keyboard key behaviour.

I know it is difficult to present an intermittent problem like this to the store but at least make them aware that it still happens and that they have a note about it. It is most likely that it will happen more frequently and then just not work at all, which will probably mean the whole keyboard will need replaced, and you didn't pay for that to happen.

Sorry if I am being ultra negative but I would really angle for a replacement before too much time goes by.

Ok me again, just a thought, it is okay of course to notify them by phone but personally I would go in person and see them physically making a note about your problem and that they also give you a copy of that note so that you have a hard copy of the issue and the measures with a time line that have already been taken to resolve it. If you can present them with written details of your purchase and the first and subsequent times you have flagged the issue and any repairs that have been done that would go a long way to them having to give you a new like for like replacement.