This morning, my 950XL was at 7% battery, after being plugged in overnight. Turned the usb-c over and plugged it back in; charging now? I don't know if I neglected to insert the usb-c properly last night or not, but I will definately keep a keen eye on the charging procedure tonight.
Update: after 1 hour on the OEM charger brought the battery to 97%.
So, it has definitely happened again...almost!
Last night I put my 950XL (DS, USA) of the OEM Charger, checked to see if the charging icon was flashing, it was not; so:
+ I tried flipping the USB-C connector around (a number of times)...No Change.
+ I tried a different wall outlet...No Change.
+ While still plugged into the last tried wall outlet, I did a soft-reset; it took a while, but when the phone restarted the charging icon was present and flashing. I then removed the charger from the current electrical outlet, and plugged it back into its usual charging outlet; again, the charging icon was present and flashing.
This occurrence is most likely what happened to me the first time (when the phone was plugged in all night, and totally discharged the following morning).
Update: happened again this morning; I believe it is happening once the battery's charge falls below a certain threshold; maybe 18-25% charge?