Unable to create file or filename of specific name in linux directory (openwrt)

Neither folders nor directories named mi_box can be created.
Other filename files and directories can be created normally.
File permissions are 777.
The user is root.
The system is based on OpenWRT with Linux kernel.
The file is on the external hard disk that is mounted.
The file path is /mnt/sda.
The error message when using the mkdir command is

mkdir: unable to create directory 'mi_box': No error information

Linux version 5.4.164 (jenkins@b411ceff8ed5) (gcc version 7.5.0 (OpenWrt GCC 7.5.0 unknown)) #0 SMP PREEMPT Wed Sep 13 03:47:25 2023

The physical device is Xiaomi router BE7000.

I’ve tried creating the directory with another name and renaming it mi_box
The error message is

mv: can't stat 'mi_box': No error information

I also tried creating a file for mi_box
The error message is

touch: mi_box: No error information

I hope to be able to create the “mi_box” directory under the /mnt/sda path and have normal read-write access to the directory and its contents.