Closing the device sometimes leaves the device in a
'bad state'. (The only way to correct the 'bad state'
seems to be pushing the reset button or disconnecting
and powering down the device.)
The commands issued before releasing the device appear
to affect the device's state. Which commands cause
problems are apparently arbitrary: such as uploading
'unicode.o', but you will only be able to tell after
you've released the device and tried to use it again.