If a firmware flash fails, a log with the error message is written to the SDCARD by the bootloader, and can be easily opened with notepad.
These kind of messages can appear:
sprite update error: checksum is error d馃錮馃鍃馃錪馃錪馃錪馃錶馃錦馃?郚?_-?
sprite update error: current card sprite failed
now hold the machine