I have a problem. I have a hex file. About one year later, it doesn't work after downloading to MCU,There are no changes to this hex.MCU is STM32F103C8T6

[YSenl.1]

About one year later,my hex file doesn't work after downloading to MCU(STM32F103C8T6),but every use is normal throughout the year,the hex file has no changes.but it's OK to regenerate ithe hex again.Why?

[ONadr.1]

There are only four options.

1.The contents of the file have changed unnoticed (rarely when saved to SSD or Flash)

2.MCU is defective

3.MCU series has some BUG (see ERRATA for used MCU series)

4.The HW around the MCU has changed and the problem is in it.

[TDK]

I would argue there is a fifth explanation:

5. Assumptions are incorrect.

Hard to know what "doesn't work" means.

[Tesla DeLorean]

Check you haven't left BOOT0 HIGH, and on F1's perhaps what BOOT1 is set to.

[Piranha]

Flash memory (when erasing and writing it), capacitors and crystals age. Voltages, temperature, humidity change. All of these and other things can change some timings slightly and then broken code can fail. Therefore it can be even a software bug.

[S.Ma]

Or the chip is a 99% clone...?