Recording "next part" erases the first part

This must be something simple that I’m missing. I’m new, so forgive my stupidity!

I initiate the Beatbuddy and record part A. I stop and hit “next part” and restart the Beatbuddy. I then record part B. I then stop the Beatbuddy and subsequently restart the Beatbuddy to play back what I have recorded.

I am left with only part B.