This is a fix for the problem that the file name is garbled when downloading a file with a file name containing Japanese characters.
When a student uploads a file with a Japanese filename, the characters are garbled when the teacher downloads it.
I uploaded the modified source to GitHub.
https://github.com/kodamayamazaki/moodle/commit/ed5e948a9da12e149a923ea15383dd8ab6504b29

How to confirm lib/csvlib.class.php

1. Added "Database" activity in the course. Use Japanese for activity names.
2. Open the added Database activity and add an appropriate field from "Create a new field".
3. Click the "Database" tab to display the list view screen.
4. Click the "Add Entry" button, enter appropriate values ​​on the "New Entry" screen, and click the "Save" button.
5. As the screen changes, click the "Export entries" button to download the file.
6. Leave the Export format as CSV and click the Export entries button.

How to confirm lib/excellib.class.php

1. Added "Feedback" activity in courses. Use Japanese for activity names.
2. Add a question from "Edit questions".
3. Answer from "Answer the questions".
4. Go back to the top of the feedback and click the "Analysis" tab to display the analysis screen.
5. Click the "Export to Excel" button.

How to confirm lib/filelib.php

1. Enter a course with a Japanese name and click the "Grades" tab.
2. Select "Export" from the report selection.
3. Change the file type to "XML file".
4. Click the "Download" button.

1. Added "Assignment" activity in courses. Select "File submissions" for Submission types and create an Assignment.
2. Click the Add submission button to upload a file with a Japanese filename.
3. A list of uploaded files will be displayed on the screen, so click on the file to download the file.

Any Japanese can be used for this confirmation.
For Example : "あいうえお.pdf"