Problem with incorrect file types (case 13902)

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On two different computers, the program worked successfully for several participants. Then both ended up tripping up on different parts of the program with different error signals.

On one computer the signal said that the exp file called practice_directrt was a "bad file name or type." On another computer the error said that the file was ?incorrect file type?. It said that I needed to change the file to the appropriate three-letter format when it ran the exp file called file1.
I am not sure what these things and I don?t understand why it only starts giving me these errors after the program has successfully ran without an issue previously.

The files for the program are attached.

Thanks!