Check your device hardware version on the lable of the back of the device before upgrade! A version firmware is for the A version hardware which is alredy EOL. B version firmware is for the B version of hardware which has a larger flash memory. Flashing the A hardware version with the B firmware version might cause audio and stability issues with your device. After such an upgrade, downgrading is not supported and might cause your device to become unresposive which can be fixed only be serial port upgrade. If in doubt, please consult your local technical support.