Some songs won't appear on playlists once exported to Walkman

[Chamomile]

Hi, tech noob here.
Any help will be greatly appreciated!

Question:
How can I fix the issue of some songs disappearing from playlists once exported from MusicBee to Walkman?

Background information:
The songs that won't appear on playlists on Walkman do exist both in MusicBee library and Walkman, and I can listen to them individually with no problem when I clicked on them.
On MusicBee library, the playlists work fine, playing all songs including said files.
I can also add and remove said files on the playlist.
They just won't show up on playlists on my Walkman.

I only use MusicBee to edit files on my Walkman.
Therefore, I import files from Walkman using "File > Add files to library" and edit imported files on a library whose music file path is directed from E:\ to E:\.
This system caused me no problem for 2 months now, until this issue with missing songs on playlist suddenly emerged this week.

Hit me with questions if you need additional information!

[phred]

What version of MB are you using? (Help > About)
How was MB installed? (Store, Installer, Portable)
Is it the same songs that don't show up, or is it random?
How are you getting your files from MB to the Walkman?
Please paste a few lines from the playlist file that show the "missing" walkman files.

[Chamomile]

Thank you for your comment, phred!
Here're the answers to your questions;

1. I'm using the version 3.4.8033.
2. MB was installed via installer (https://www.getmusicbee.com/).
3. It's always the same songs that don't show up on my Walkman playlist. They're some of the newest additions to my library.
4. Here's how I send files from MB to my Walkman: right-click on the file in MB > Send to > Device WALKMAN (E:).

Finally, I'm sorry I couldn't understand exactly what you wanted in the last request.
Would you clarify what you meant by "lines," especially?

Again, thank you for your help!

[phred]

Would you clarify what you meant by "lines," especially?

Thanks for the additional information.
A playlist is nothing more than a text file which contains the path to the music file. Using a text editor (Windows WordPad) open up the playlist. You'll see lines for each music file. Find one of the files that don't appear on the walkman and copy the entire line and paste it here as a reply.

[Chamomile]

Thank you for the clarification!
I managed to open the playlist on WordPad, but I can't tell which line refers to which song since all I see is a block of continuous texts...
Looking at patterns of texts, here's what I suppose you wanted;

E:\Music\NWWM_REC\2022-04-29\015-1842.MP3)

If this wasn't the information you needed, please let me know!

[phred]

E:\Music\NWWM_REC\2022-04-29\015-1842.MP3)

This might be a clue.
What language are you using on your PC/MB?
What format are your playlists? (What's the file extension?)

There appear to be four characters after the file extension (.MP3) which shouldn't be there.
A similar line from one of my .pls playlists looks like this:
Z:\Music_Files\Rolling Stones\With Special Guests Live 1975-2019\7-4 - Champange & Reefer (feat. Eric Clapton).mp3
The .mp3 should be the last thing on the line.

In case those four characters get re-encoded properly on your machine, this is what they look like here:

[Chamomile]

I'm glad my information helped!

I'm using English on MB, and Japanese on my computer.
According to the property info, playlists on my Walkman are saved as M3U files.
I don't know how to inspect the format of playlists on MB, so please let me know how if you need that information!

Looking at the WordPad texts, every song on the playlist seems to have those 4 squares at the end, including the songs that do appear on my Walkman playlists.
Should I change the format of my playlists?