I purchased a 64GB Sandisk USB thumb drive to replace an old iPhone as a music source. I initially transferred about 45GB of music to the drive. When first inserted into the USB port in the arm rest (2018 230i) iDrive found all the music on the drive. Subsequently I found additional music files I wanted in the car. I pulled the thumb drive, stuck it into my desktop computer, and added the extra folders of music. When I plugged the thumb drive back into the car iDrive did not display the new files. Searching for them failed. Navigating the folders manually failed. I tried renaming the volume to see if that would cause iDrive to rescan the thumb drive. Nothing. I tried reformatting the drive and copying the files back onto it. No improvement. Apparently iDrive is unable or unwilling to refresh its content list for the device. I have no idea how to force it to do so. There are about 4,800 files on the drive in mp3 and mp4 formats with varying bit rate encodings. All the files originally on the drive work fine regardless of their encoding or bit rates. Any ideas on how to force iDrive to see the additional files?