After trying all the recommended fixes for this issue in all the different forums I could find (new cables, privacy setting resets, full system reset etc) I still had the problem so I have come up with a work around. I now plug all my devices - iPad, iPhone - in to a USB multiport and then connect the multiport’s USB cable to my MacBook air. Problem solved! I’m using the Belkin 4-Port USB 3.0 Powered Hub! - Which I’ve plugged in to power as well as to my Mac. Basically, letting the Hub power my devices Vs my Mac.