Help! Files dissapearing from sd card after plugging into phone

I'm trying to copy songs from my computer to my phone's external microsd card. I'm using an sd-card adapter for the transfer. The files copy successfully and I can play them from the sd card. However, the moment I plug the card into my phone, most or all of the files dissapear. My music player cant find any of them, and my file manager shows the directory I put them in as empty. If I reconnect the card to my computer after this, I will find several gigabytes of data in a directory called LOST.DIR even though I had emptied this directory previously. It would seem that my phone is throwing these files out during the "checking sd card for errors" process. The amount of data in LOST.DIR is not enough to account for the missing files however.

Also, not sure if this is related but, while copying the files I would get an error saying it is trying to copy a folder named "(null)" to "(null) and I would get an option to skip or merge the folders. Regardless of what I choose, the end result is that I will get some folders on the sdcard with names that are "blank" or made entirely out of underscores. The original copies of these folders had names with Chinese characters. A screenshot of this is below.

Any help with this would be nice, as right now I have no way to copy songs onto my phone. My phone is running android 4.4.4 Cyanogenmod. My computer is running Ubuntu.