I will manually cancel the extra Invoices. I would have already cancelled one, but I was afraid I would make things even more confusing since the email notifications are so sporadic. I didn't want a notification to arrive for one and not the other, and then the one someone receives is cancelled. I guess Paypal is having some glitches somewhere along the way, but it seems to be limited to the notifications alone, payments being made are going through just fine.
I just happened to be browsing SPs new Dunhill pipes and there was this four panel billiard for $780 and it wasn't nearly as nice looking as what we're getting from Alden Pipes!