Send AT&F (factory reset) followed by AT&W (write settings). This clears any inconsistent NVRAM values from the old firmware.
: The module’s status light turned a solid, terrifying amber. For sixty seconds, the system was a "black box"—dead to the world. ml7820 b firmware
If you can confirm the (e.g., printer, computer, or industrial tool), I can provide the exact version numbers and direct download steps. Send AT&F (factory reset) followed by AT&W (write settings)