VLC Android (v3.4.2) not displaying subtitles from external usb storage device on Tablet.

On playing video files with both internal and external subtitles, VLC displays all available subtitles when the video files are located in either the internal storage or sd card. But, when the same files are played from an external usb storage device attached to the tablet via USB-C port, the subtitles do not display at all. I have tried with 3 different subtitle files types - srt and vtt file alongside with mp4 video files as well as mkv files with inbuilt subtitles.