I have a brand new 2023 Jeep Grand Cherokee Limited and the USB will only recognize 233 songs out of 7000 on the San Disk 32 Thumb Drive. My old 2015 Jeep Grand Cherokee Limited was able to recognize and play all 7000 songs. This does not compute.
If you’ve tried 2 thumb drives … San Disk and Lexer (which you posted on the jeep forums)
Then there’s something the 2023 Jeep doesn’t support about them.
What it doesn’t like is anyone’s guess ? 
All you can try is experimenting with different file system formats … eg FAT32, exFAT, NTFS etc
and different partition tables … eg. MBR or GPT (Master Boot Record / GUID Partition Table) … GPT is the newer standard.
eg. if the USB Drives are MBR, format them GPT or if GPT, then format them MBR
Make sure you have all your songs backed up, as formatting file systems and partition tables wipe the thumb drives.
Also, what format are your songs ? eg. MP3, FLAC, M4A etc etc and the Bit Rates
Do the “missing” songs have something in common ? are they the same format ? are they over a certain bitrate.
Basically you have to do some investigation and experimenting to find out what Jeep Grand Cherokee changed from the 2015 model to the 2023 model.
