I can confirm that the red led was lit all the time when in bootloader mode. I still couldn't see it via nRF Connect.
I failed to connect via the serial console on either board - due to my poor attempts at wiring and not wanting to make a mistake and damage the board(s).
I couldn't see anything different between the working board and the bad board but have uploaded three files:
1) good puck left - bad puck right.jpg.
2) bad puck - side view.jpg
3) bad puck - top view.jpg. (different lighting conditions).