Latching relay seems to be turning off and on rapidly

I am wanting to make a latching relay. I supply power from the normally on pin through the com pin to the activating pin. I was expecting it to turn on and stay on. But instead it clicks repeatedly as if its turning off and on.

http://www.nteinc.com/relay_web/pdf/R25.pdf

That's the relay i'm using.

If I use the normally off pin for my power, run com to the activation pin, it clicks once and stays on. But it doesn't with the normally on pin.

What gives?

latching relay