When exporting a course to IMS and restoring it back, the settings for the tests (quiz) are lost when reimporting them back.

This alone could be overcome if at least common tests settings (as described here where used, but it is not the case. Common quiz settings are used when you create a new test, but not when importing a test from a IMS CC archive. Normal behaviour would be that common settings are used by default when importing quizzes from any format as long as the imported tests do not specify any (which is the case for IMS QTI format).