That is quite possible, the antenna is glued to the case and contacted by a spring contact on the mainboard. So it may have just corroded a bit if you had at some point humidity in your watch.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Maybe I will just try to disassemble it for fun. Maybe it will fix the bluetooth also ^^