Resolved! Two different STM32U031K8U6 MCU have randomly entered RDP 1 mode without instructions to do so.
I have been looking at the power consumption on an STM32U031K8U6 when it is put into standby mode with the RTC setup to regularly wake up the processor. Most recently I had the wake-up time set to 250ms. The processor wakes up and does the following-...