iPod classic (120GB, 7th gen) not showing music when ejected

My iPod classic (7th gen, 120gb, model A1238) shows no music after ejecting. You can load a few song to it, eject it and it will work fine. However, if you reconnect it and try to add more songs to it they all disappear after ejecting. You can see them on the iPod in iTunes and see the space they take up on the card when right clicking "Properties." This issue started with the original hard disk drive so I assumed the drive had failed after all the years of use. I replaced it with an iFlash solo and a SanDisk Extreme Pro 128gb, SDXC, 170MB/s SD card (which is known to be a tested and compatible card) formatted to exFAT32. The problem still persists. I am suspicious that the issue might be a synching problem with either iTunes (v12.10.11.2) or the firmware version for the iPod (2.0.1 PC). I'm running Windows 8.1 on a Dell Inspiron. Any ideas on what the issue is? It still technically "works" but you can only play songs from the first two or three synching sessions. After that, you have to restore it every time. Video playback works but longer movies will freeze and crash back to the main menu. I have a working 30gb, 5th gen iPod Video with its original HD drive but I'm afraid to connect it to see if crashes too.