Вот тут "Unbricking A SEGGER J-Link V9 Debug Probe" (см. ссылку) в
комментах отметился Rolf Segger: "...Why the CPU lost its memory we never figured out, but I think this is a problem on many MCUs. Some are better in this respect than others. On the current models (V10/V11), to the best of my knowledge this has not happened at all, and we are using the LPC4322 for about 5 years now..."
v9 это STM32F205RC.
Похоже на то что если хочется стабильности, не надо вообще трогать FLASH. Только внешний EEPROM.
https://hackaday.com/2020/12/30/unbricking-a-segger-j-link-v9-debug-probe/