stm32f4 flash operation not stable.sometimes the write operation cannot be success!

[xqing.1]

Any attempt to read the Flash memory on STM32F4xx while it is being written or erased, 

causes the bus to stall. Read operations are processed correctly once the program 

operation has completed. This means that code or data fetches cannot be performed while 

a write/erase operation is ongoing.

How to protect it？？？

[GLASS]

Dualbank flash is the more efficient solution​.

you can also relocate critical SW (isr, all flash write functions, etc...) in RAM.

[xqing.1]

https://community.st.com/s/question/0D50X0000A4qiL0SQI/why-would-flashflagpgperr-and-flashflagpgserr-be-set-after-a-successful-flash-write-and-at-powerup-before-any-flash-write-operations

[xqing.1]

https://community.st.com/s/question/0D50X00009XkWriSAF/stm32f407-flash-programming-error-pgserr-and-pgperr