I've been having this issue for about a week now
I'm using Musicbee previously on version 3.3, now on the latest 3.4.7805
I downloaded a patch a little while ago but not sure how much good that did I've been having this issue on every version I've used
I'm using Windows 7 Ultimate and the phone I'm transferring to is a Sony Xperia 1 II
Now with all that said, the issue is I've been trying to transfer my 400gb or so worth of songs onto my Micro SD cards for weeks now. One is a 1tb PNY card, the other is a 512gb SanDisk. I'll give a small timeline too
First attempt I try transferring to the PNY card. MusicBee shows errors when transferring and says it couldn't transfer literally everything that it tried to, it just created empty folders
I go into the files and fix a few things then try again
Then I hear PNY cards are a bit faulty so I try the SanDisk one now too
Transfer files to both, MusicBee sees no issues, so I think I'm all good, until I check the files and see it's all blank folders but space is still being used
At this point I don't know what's going on so I update from 3.3 to 3.4 and try a patch. Same thing happens.
Just to make sure there's no issues with the cards, I transfer my other files like pictures and books to it, and those stay in there fine but not the music
Just to make sure it's not MusicBee again, I see if it's my phone that can't read it.
I put the SD card in my phone and it gets the books and pictures fine but no music
Then I try downloading the files individually or in batches. That's been hit or miss. Most recently the batch I downloaded, so like 10 albums at once, that way fine, but the additional ones I added individually haven't shown up.
I'll take the SD card out after a download and put them back in to see if they stay, sometimes they do and sometimes they don't
The most concerning thing of all is that it still takes up space every time. So I've been constantly having to wipe the cards.
At this point I have no idea what the issue could be. I've updated to the latest version as of this post and it's still happening. Sometimes I wonder if it's the size of the library but that honestly was never an issue before, it's only a recent development, so perhaps the issue is the phone. It did just come out last year but God only knows what the real issue might be.
If anyone has a solution or a similar problem please let me know. Last thing in gonna try is just transferring from the direct music folder then finally figure out if it's my phone or MusicBee, or hell maybe even my SD cards could be that both are somehow faulty. I'll post results here later, I'm currently on mobile