STM32F417 flash spontaneously erased?

[CBrad.2]

Hi,

We have a product in the field using STM32F417ZG, and it was returned to us after it mysteriously stopped working. On receiving the board, we noticed that nothing was running on the STM32F417. We read out the flash memory and it appeared to be erased (0xFFs). Important to note that we don't enable read-out protection. We reprogrammed the MCU and it started working again as normal, and a read-out of the flash was as expected. Does anyone know how this might have occurred?

We have also encountered one other device where the read-out protection was enabled but we have never explicitly set it during programming, although we can't rule out that someone enabled it accidentally during initial programming.

We are using the built in DFU bootloader via USB and originally were using the DfUSe Demo app before STM32CubeProgrammer was released.

Thanks,

Chris

[PChao.2]

We don't really do much with the option bytes though.  Also the devices work for 3-4 years with no issues but then they just stop working because the flash erased itself somehow.

[Tesla DeLorean]

Had products prior with F2/F4, and F1, a handful hit my desk.

Power supply, esd or glitching events could likely initiate. At the end of the day a single "go" signal initiates the sequences. Or technicians trying to "fix" things, or speed things along. Getting frustrated and impatient with update speed or procedures.

I'm sure ST's got some metrics or failure-analysis reports on the phenomenon