i am not sure is it of your case, sometines i will get the device not to be connected but not all the times. After i moved all files from internal storage to sandisk class 10 64G SD card, the case not happen again.
In fact it can't be my case... on other PCs it works fine, on mine it doesn't want to connect. For now I'm keeping the 5 inch and I gave the 8.8 to my daughter. Anyway thanks for the help.
I have the same problem as well...