I had this happen to mine, and it was the clincher in getting me to return it. Unfortunately at the time I both needed the pen and was showing off the handwriting to a customer. I also had issues with palm rejection and wasn't a fan of the writing compared to the SP2.
Looking at the number of threads about the pen, I'd say the pen itself is going to cause users some grief. It is another lot of electronics to go wrong unlike the passive pen of earlier models.
I'm not sure what caused this to happen but it happened twice during the day and the problem resolved each time. It had up until then not done this for over the week I had it.
One thread just posted the O.P. Had a writing pressure issue eventually solved by pulling the tip out and replacing it. Aside from battery replacement this is about the only other thing you can do.
Maybe you should post a poll and see how common this is? It could we both were experiencing faults others haven't had or it could be just a normal but undesired feature of the pen that surfaces sometimes.
I wonder too if these pens are subject to electronic interference from other nearby devices.
