[jakeru]

three things to try:
1. Open it up and replace the battery (try this first)
2. Replace the momentary push button switches (do this after replacing battery, if light on the key doesn't blink reliably when pressing a button)
3. To fix unreliable/intermittent operation when the light is reliably blinking, try reflowing all the solder joints on the circuit board. To do this, desolder and temporarily remove the battery holder. Then reflow solder connections underneath, and replace and resolder battery holder. A small/precision soldering iron is recommended to reflow connections of the small surface mount components.

Good luck!