Hi, thank you for your shared files! I'll carefully take them for reference.
In fact, the occurred problem about Nihon file import are related to the device version, which has been reported for days, as shown in EEG-1200A V01.00 by jacobshaw42 · Pull Request #11431 · mne-tools/mne-python · GitHub.
Brainstorm shows ability of importing such files by updating its supported file formats through reverse engineering: Error message when "Reviewing raw file" for the EDF files generated by Nihon Kohden - #10 by lyngen.
Due to some business confidential reasons, the example data may not be provided, much sorry for this.
Also appreciate if you can keep updating some information for this problem, thanks!