The HTML generated on a submission .html file when you download it using "download all button submissions" on online text assignments don´t have any HTML HEAD meta charset tag, so when you open it on a browser there are a lot of character error on language like French because there is no charset defined.
The bug is generated on: moodle/mod/assign/submission/onlinetext/locallib.php, line: 229, as you can see in this code there is no html head:
It can be solve using this line:
I think there is another way to solve this issue, but it works for online-text assignments.
what do you think?