Why does the python os library return an error on one file but not three others?

The simple script to collect file names and sizes fails on the 4th file with the following error:

"FileNotFoundError: [WinError 2] The system cannot find the file specified: 'A023_04.mp3'"

import ossiteID = 'A023' #This must match audio and NVSPL directories and filenamesdrive_audio = "E"dirName_audio = drive_audio +':\\data\\audio\\'+ siteID +'\\'fileNames_MP3 = [file for file in os.listdir(dirName_audio)] # this works:for val in fileNames_MP3:    print(val)print('\n')# this works for the first three files:for val in fileNames_MP3:    file_stats=os.stat(val)    print(val, file_stats.st_size)

Here is the output:

A023_01.mp3A023_02.mp3A023_03.mp3A023_04.mp3A023_01.mp3 1073672486A023_02.mp3 1073644272A023_03.mp3 1073644273Traceback (most recent call last):  File "E:\data\mp3_garage\funWithFileInfo.py", line 16, in <module>    file_stats=os.stat(val)FileNotFoundError: [WinError 2] The system cannot find the file specified: 'A023_04.mp3'

I am able to view the properties using the Windows file manager, and don't see anything quirky about that particular file compared to the others.