Blinkt fails after a week


I have a project that includes a Blinkt on a Raspberry Pi Zero W (with pre-soldered header). Everything worked perfectly for a week or so, but then the Blinkt just stopped working - ie no LEDs ever turn on. (Went on the blinkt, I suppose…) This happened while the unit was in its 3d printed enclosure and screwed shut, so shouldn’t have experienced any particular mechanical stress.

Swapping it out for a different Blinkt unit restored functionality, and the defective unit doesn’t light up at all in a different Pi Zero W.

Some non-Blinkt GPIO pins are soldered underneath the Pi for LEDs or switches. Power is from a Nokia DC-18 power bank, with the on/off contacts exposed as power switch - the Pi itself operates with zero software glitches with this arrangement. Picture below.

Any ideas what might have gone wrong?