Puck sending same key repeatedly?

Hmm - that is strange. Removing console.log may really help - you could always move the console to a different device, but Espruino will always try and send the data on BLE if it thinks it is connected.

Does something like NRF.setConnectionInterval(100) fix it for you? It might be related to the connection interval stuff I mentioned.

Worst case you can add something like this:

http://www.espruino.com/Reference#l_E_enableWatchdog

If Espruino really is being unresponsive then using the watchdog would ensure that it always stays working. If you put it in manual mode the hardware itself will reboot unless your code explicitly calls E.kickWatchdog every so often.