China DOS Union

After returning to work after a long holiday, I turned on my Tsinghua Tongfang E700. When it reached the protection card timing link, the "bad command or filename" message appeared, and the computer got stuck and wouldn't move. There was a cursor flashing below. I pressed F10 to try to enter the protection card settings, but there was no response at all.

The protection card of this kind of computer is built into the BIOS and cannot be disabled.
When I entered the BIOS settings to boot from the USB drive first, it was still stuck at the "bad command or filename" and couldn't reach the USB drive boot link.
Did I enter DOS? I tried the DIR command, and indeed a large number of BAT, EXE, COM files could be seen.
Using the VER command, I could see that the version was DOS 5.0, which is also rare.
Using the PROMPT $P$G command, an A:\ prompt appeared.
Using the type autoexec.bat command, I couldn't see the content, and using the type config.sys, I could see the content.
I couldn't find any TXT - like files inside. I ran several BAT, EXE, and COM files, some didn't display and some crashed.
After trying for several hours, I finally found that running base.exe could bring up the protection card interface, then pressing F10 could enter the protection card settings, and immediately uninstall the protection card.
I restarted the computer, the protection card installation interface appeared, reinstalled the protection card software, and then set it up properly, and the problem was solved.
Afterwards, I thought that maybe the autoexec.bat was damaged, and maybe rebuilding an autoexec.bat and writing base.exe in it could fix it, but there was no chance to try it.
I didn't expect that after many years, there would still be a chance to use DOS.