usbd prevents iPhone 6S charging on mid-2015 MBP

What is the usbd process? Yes, I can guess what it stands for but I haven't been able to find any information on it and all I know is that its running prevents my iPhone 6S running iOS 11 from charging on any USB port of my mid- MacBook Pro running High Sierra.

The issue is identical to the one described in the thread MacBook Air Not Charging iPhone 7

When I plug the USB cable into my MacBook (both Ports), and then plug the lightning cable into my iPhone [6S], the iPhone flashes between charging and uncharging, perhaps each second... Another way to put it is, that the iPhone is vibrating every second, because it is constantly charging, and then not charging.

with the difference being that in my case force-quitting the usbd-process (and re-force-quitting it when it occasionally respawns) solves the problem immediately.

So the response by Kappy in the aforementioned thread is incorrect: The USB port of the MBPro provides plenty power to charge the iPhone - but whatever that daemon process does interferes with charging and more importantly also with synching, data transfer etc. Not even unlocking the iPhone or the SIM is possible when it is auto-toggling between the charging/non-charging on the USB port.

With every toggle in charging state, the iPhone also emits the "charging" audio signal and vibration, neither of which can be disabled, making this bug obvious and supremely annoying because a low-battery iPhone cannot not really be charged incrementally in spite of the bug, as the constant "ding" drives everyone in the vicinity to insanity.

Can anyone help?