I don't profess to know the answer, but it seems there is a Random mode than can be turned on / off. It is button number 7 in the image below.

The manual states: "7.Random Button: In CD Mode, press this button to cycle through Normal Play Mode, Single Play Mode, and Random Play Mode. In USB Mode, press this button to turn Random Play Mode on or off. See Operation >Playing Audio CDs or Playing Audio Files for more information."

My suggestion is to press this button until Random Play mode shows Off, then try to select and play the required audio file.

The manual is vague in selecting specific files, unfortunately (I included the version I checked in the attachments).

Hope this helps in some way.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
2021-01-30_1-15-01.jpg (47.75 KB, 98 downloads)
DN-300C_UserGuide_V1.0.pdf (1.08 MB, 2 downloads)
BIAB & RB2025 Win.(Audiophile), Sonar Platinum, Cakewalk by Bandlab, Izotope Prod.Bundle, Roland RD-1000, Synthogy Ivory, Kontakt, Focusrite 18i20, KetronSD2, NS40M Monitors, Pioneer Active Monitors, AKG K271 Studio H'phones