I had a slightly different issue. The end of my pen has some small shaving of plastic that doesn't give me a good point. Is that something MS would replace? I suppose I could use a file to shave that little piece off but I am afraid it would do more harm than good. It's not big just annoying.
Well, after my previous post it worked flawlessly until today (13 days), when it started acting up again. First time I restarted the tablet, second time I had to remove and re-insert the battery to get it working again. I refuse to believe that Microsoft is sending us ten year old batteries, mine is dated to 2018, if I'm reading the battery label correctly. I guess I'll call Microsoft and ask for a new pen.
Just posting update to add to the community knowledge base.
To check a battery correctly, you really should use a battery tester which puts a slight load on it during the test. You can get a false positive reading with a voltmeter without having a load on the battery.