Default [Q] Random freezes, and tasker asks about nonexistent USB device?

My Note 2 has been freezing randomly, often while the screen is switched off (nothing would wake it....sometimes it responds again after a few minutes). This happens several times a day. At first I tried wiping and installing a clean rom installation (although i just swapped Phoenix ROM 15.7 for 16.7) but to no avail. I also have Tasker installed and on booting it has now begun asking me to run Tasker every time this usb device is plugged in (but there is no usb device plugged in). Any tips on how to troubleshoot please?