Disallow downgrades below v1.3.0 due to EEPROM layout changes (check via register 0x3E – layout version).
Some users prefer replacing the AOT-4221SR with other models like the ZTE F670L for better Wi-Fi coverage and more open configuration options. Firmware upgrade via command line - Teltonika Networks Wiki aot4221sr firmware upgrade
Ensure the file extension matches the requirements (typically .bin , .img , or .tar.gz ). Disallow downgrades below v1