@nhatkhoa102:
Okay, I couldn't reproduce any issues with an SD card on my end,
but I did update the USBMS tool to be more user-friendly in case the SD card is busy, so, try again after replacing the tool with this one.
(Just replace the file in the koreader/data folder, don't unpack the archive or anything
).
Assuming something is actually holding on to the SD card, you'll get actionable feedback on-screen instead of a shutdown