Default PAC-Man ROM, phone won't read half of SD Card?

Hi guys, I flashed PAC-Man ROM a few days ago (Not sure if this is related, but including it anyways) and I have a 64 GB SD Card installed on my 16GB S4 GT i9505. I noticed just recently that my phone only reads half of my SD card for some reason. When I plug my SD card straight into my PC, I can see all of the folders in it. However, when I plug my phone into my PC and try to read the SD card contents like that, I can't see over 3/4 of its contents. Moreover, I can see the files just fine on FX and any other file browser, but my music player won't detect that there's any music on my phone (My music is one of the folders that doesn't show up when I view my phone via PC)

I tried formatting the SD card, but to no use.

Can anyone help me or tell me what to do please? Is it a partition thing? Thank you for your time.