No SOLUTION for me as I STILL have the same problem after 5 months and truly countless hours. That said, I have found further information that may help one or more of you. When you type the *#7284# (or *#3424# on older/other phones) there may be a single button shown labelled "Qualcomm USB Settings" below everything else, no options, just the button. Tap on that, if it's there, and you should go to a new window that shows a number of options: MTP, MTP+ADB, PTP, PTP+ADB, RNDIS+DM+MODEM, DM+MODEM+ADB. If it does not, "Save and Reset" and when phone rebooted and stably running again, try *#0808# that MAY bring you to the "USBSettings" menu where the USB settings for: modem direct (CP), and Application Process (AP) settings (as i poorly understand it, essentially changes which processor will handle requests) can be made independent of the UART/USB menu. Below this on the same page there should be an area with the other settings not shown in the UART/USB menu (same choices as the long list above, plus one). if you need full service mode that code is often *#0011#