Problems with recording after playing a file

[max1605]

I have adapted the code so that a recording from the SD card is played first and then a recording is made after a pause of 500ms.

Playback works without any problems.
During the recording, it also shows how many samples have been written and the file on the SD card has the corresponding size at the end of the recording.
But when I try to play the file, there is no sound. Audacity doesn't show any waves either, just a straight line.

If I remove the playback option in the code before recording, it records a file that can be played back. Audacity then also correctly displays the waves.

Has anyone ever encountered this problem and is there a solution?

Thank you very much!