: Data is pushed to the chip starting at address 0x0000 .

If a Flash verification routine (e.g., CRC check, checksum, or simple read-after-write test) fails at this address, the CPU may immediately execute garbage instructions, causing a hard fault or watchdog reset.

Voltage fluctuations during programming can trigger a reset. If the voltage isn't stable at the moment of the first write, address 0h will fail.

The most common cause. If a firmware flash operation loses power, experiences a communication glitch (over JTAG, SWD, or UART), or is aborted mid-write, the first sectors (including block 0) are often left in an indeterminate state. Since the bootloader vector resides in sector 0, an incomplete write to sector 0 triggers this error immediately on reboot.