ipod nano running app crash

I use an ipod nano 7th generation for running, mainly. Recently, the Nike+ app crashes with a full reboot of the ipod. The run is not saved and not transferred to Nike+ webpage.

The crash happens typically right after an announcement of a completed kilometer. I have set my ipod to metric and run in the "distance" mode. I use a bluetooth heart rate monitor and I did not connect Nike+ sport kit.

Restoring to factory settings did not help.

Thanks for your help.