The problem with ESD (and overheating during soldering) is that, sometimes it does not immediately kill the chip, but it degrades it causing curious behavior. Some time ago, i had such a curious problem with a chip that worked perfectly fine, only that the current it was drawing during operation was abnormally high - if i remember well about 20mA with no load, and around 2 mA during sleep. After tons of senseless search, i turned to microchip and reported the fact, only to tell me that ESD or overheating during soldering can cause such behavior.
But you did not answer - the antenna has one or two wires inside?
PS I was in Austria before summer for training, in Absam near Innsbruck, Tirol, and went into a restaurant for eating, and noticed that despite being thursday night the restaurant was full of people. And then, suddenly, a crazy mob wearing costumes and making noise went into the restaurant. Some where dancing, others dressed like witches were screaming, and then there was this guy dressed like a bear, chained to a brutal fat dude with a club.... And everyone were going around the people, hitting them in the back and giving them a liqueur to drink. Definitely the best day of the best trip I've ever made so far!!! I think it was called Absam Matchgerer