Resolved! STM32L4xx board has GPIO pin 5 on two different ports (GPIOA and GPIOB) that need to interrupt at different phases of processing. How to initialize PA5 to interrupt initially and the switch to PB5 until done and switch back?
EE designed the board with both pins in use and both needing to wake up from STOP2. At start PA5 must be used to awake. Once awake, switch interrupt to PB5 for normal processing. When normal processing is done, switch back to PA5 and enter STOP2. ...