Saving Record Buffer does not work

Saving Record Buffer does not work i think
i am using Nebulae v2.1.2

in the manual it says:
“Saving The Buffer To USB: To save your recorded buffer to your USB drive, hold the File button
and press Freeze button. This will save the buffer to your USB drive as a .wav file, allowing you to
revisit the buffer in File mode, or export it to use in a DAW or other audio playback device.”

I tried it with different USB Sticks
there was never a recording or a new wav on the stick

Did i miss something or is there a trick?