7th generation nano unexpectedly restarts when connected to bluetooth speakers

1. connect to bluetooth speaker, start playing music

2. disconnect from speaker (bluetooth on->off->on on nano)

3. connect again, start playing music

4. black out the screen through power button (or wait for it to turn off), try waking up through on-screen button and it crashes.

Able to reproduce consistently in under 45 seconds with two different bluetooth speakers, with battery/power supply.

I have a video which shows back-to-back restarts if anyone not able to reproduce it.

(already went to genius bar and got it replaced,so not a hardware issue. was finally able to reproduce it tonight)

Eugene