HELP - Problems with Functionality after upgrading to flash memory

iPod Classic 160 GB (7th Gen)

I recently used the iFlash Solo kit by Tarkan and I'm running into some serious issues in using the iPod after uploading songs onto it.

My brother and I have reformatted the SD card several times (both in Mac and PC, including following these directions regarding partitions: https://www.iflash.xyz/prepare-sdxc-exfa...).

The problems we keep running into is that after we upload any significant amount of songs, the iPod shows up as empty after ejecting it from iTunes. We've tried several different methods for uploading:

• Syncing the entire library at once (there's over 11,000 songs so it takes a while, but we've tried it several times to no avail)
• Dragging songs in smaller batches (by genre)
• Dragging by album, which works some of the time, but I recently discovered after doing probably between 300-500 songs, my entire iPod showed up empty, including songs that were there on previous uploads. What's more, after this point, iTunes will no longer recognize the iPod, which leads me to restore it again.

After restoring it again, I put just a few albums on and it worked, but I'm very hesitant about uploading more since it keeps erasing the entire iPod.

Any ideas on what to try next? I am a music geek and use my iPod a lot, so it's important to me to get it working again.

Info on my iPod:

• iPod Classic 160gb (7th Gen)
• iFlash Solo conversion card by Tarkan
• 256gb SDXC 1000x card by Lexar (150mb/s transfer; 80mb/s write), Class 10

NOTE: I did order the card off of eBay from Singapore and I believe it technically holds 268 GB. I'm not sure that this card has anything to do with it because otherwise, it seems to work fine.

One last point, I replaced the battery, but I'm sure it has nothing to do with it.

Any help would be GREATLY appreciated! Thanks!