Trying to work Bosch smart radio in Campervan!

possibly music needs to be in the root folder, as in not in nested folders. Put a song outside of all folders and test to see if that works

Charging will be using a power only mode and not enabling the data lines on the USB connector.

What model number is it? This would be much easier with the manual!

When you say you can't play music while charging do you mean your phone makes no sound if you try to play or something else?

What's written on the stereo screen while you're charging the phone? That's really interesting.

It's possible your phone thinks it is playing music through the USB port. Android phones can be set to never do that, but have you cycled through the AUX and USB buttons while it's plugged in to see if you hear anything. You might try pressing each one twice to see if you get a choice like 3.5mm/USB, or USB data/USB audio. iPhones are more likely to work as an audio device through USB on older stereos.

The Bluetooth connection might be phone only and no media. If that was the case I'd expect sound to come out of the phone itself though.

Good suggestions about trying an MP3 file in the root directory. You've said your USB stick is only 2GB, so it should be compatible with everything. If you're trying in this direction try formatting the USB as FAT33 as suggested and first copy just one song over and rename it testsong.mp3 . Some devices prefer to see only 8 characters before the extension.

Cant say its a match, but looks similar, perhaps worth to go through and try according this manual

https://downloads.bosch-carmultimedia.net/file_downloads/829d9-ba_smartradio_panel_nafta_or.pdf

I'm glad! What worked ?

Oh, so it with a temper, not all "crap" USB would do 😏

Enjoy when you take it out "for a walk"