A few weeks ago we encountered an issue where the student received an error message about file upload: "The upload size of 4096Mb has been exceeded"
Yet, the submission still succeeded (student's screenshot):
The error message is misleading to the student.
We looked through the database logs but failed to find any issues. In testing we could not reproduce the issue with the original file. There were at least 3 other student reports but only for this assignment.
Due to upcoming changes in Sakai 12.x to Assignments, this may become obsolete -but reporting in case others experience this issue.