STM32WLE5 LoRaWAN --- code hangs in RTC module??

[SWenn.1]

Good morning....

Please refer to attached pics below:

I have referenced Lorawan end node code from STM32 library for the STM32WL55 to use with my custom pcb that has an STM32WLE5.  The RTC section of the code is identical to that in the reference code.  I load the firmware onto the target and it works for a day and then locks up.  Locks up is defined as no more serial comms and powering down the unit and repowering does not allow the unit to resume.  If I connect with the debugger I seem to be hung in the RTC_EnterInitMode() / Hal_GetTick function.  I have seen this on two boards now.  Can anyone tell me what might I do and what is going on??

(btw.....I do not have a structured solution on how I make it go away and rework....a myriad of rebuilding, reflashing, etc. and at some point it works again) 

[SWenn.1]

Adding context to the issue:

The module I am using is a SEEED WIO-E5 (STM32WLE5JC, with embedded 32.768khz crystal, etc.). See Figure 1. I found that by changing the .ioc file to use LSI instead of LSE and flash the board it comes back to life again and things work.

What would make the LSE stop working if it has been running for a day+ from a power supply?

https://files.seeedstudio.com/products/317990687/res/LoRa-E5%20module%20datasheet_V1.0.pdf