Error 1 occurred at Write to Text File

Hi everybody!

My state-machine should save data in file for 10 seconds when I press the Record Button and then read data again without saving.

The Random Number block will be replaced with the Analog Input of an acquisition device (myRio).

The program works but I am getting an "Error 1" at Write to Text File block in the saving loop. How could I solve it?

I've attached the VI.

Thank you in advance,

Lorenzo