I've apparently discovered a track limit of 767 in a single CD folder. In recent years I've switched from music to downloaded audio books. I prefer CD's because they remember the position and have never gotten a mp3 data-DVD to work. Regardless, I routinely take the audio book and run the mp3 files through a track splitter so that if I change disks, I don't have to sit and Fast Forward through hours of audio to get back to my restart point. I had created a single CD with multiple parts of the same book split into 3 minute tracks and all dumped into the same folder. The player wouldn't advance past the 767th track. If you look at 767 in Binary, 001011111111, then 768 is 001100000000. Clearly the player is using a 10-bit counter. The head unit is quirky because if you're playing a CD, it'll remember your position across input-source changes. The USB stick does not. So if you normally listen to a book on USB but subsequently have a passenger who wants to listen to the radio, you have to reposition the book afterwards.
767 is kind of arbitrary. But good to know if folks are just dumping all of their mp3's unorganized in one folder & have an issue. My car is my office so I pass a lot of time between sites with audiobooks. I've never had an issue with losing my spot in a long (40 to 60 minute) track. I keep the books on a USB stick that doesn't get pulled out till I need to load up another book. If I flip to FM, turn off the car, or even receive a phone call, it just picks up where I left off. If I'm in a music mood, I just play the radio or bluetooth from the phone. Pulling the USB stick will make it 'forget' it's spot in the book.
odd/ I always pull my usb stick to add/remove stuff; & I always wondered how this stereo manages to just go on where I left it the last time (in the middle of the song)
I found there to be a 255 file limit per folder. This is on a Prius Two (2013). 255 is a common number in computers as an upper limit. So, when I put MP3 files on my USB drive for the Prius, I limit the number per folder to 250-ish. This might also be an "indexing" issue. I have a Garmin GPS with MP3 storage/playback capability. Putting MP3s into subfolders of more limited quantity lets the software "boot" faster than having hundreds of MP3s in one directory.