NB. Moodle version affected : 3.0.2+ (Build: 20160225)
When importing a Common Cartridge archive (IMS CC V1P1), Moodle will fail if it contains a True/False question. The message error is : "Unknown answer identifier detected in true/false quiz question with id 1".
Some more precisions:

• The same archive will be restored without problems in Moodle 2.8.x for instance.
• The problem seems to be specifically linked to the process of True/False questions only, since restoring works well when removing all T/F questions and letting the other types.
• Import of the equivalent T/F questions works well when importing them in a Question Bank in the GIFT format. Then the tests with True/False questions will work as expected (with regards also to the other issue on T/F questions MDL-51048.
• Same problem occurs when exporting a (working well, including T/F questions) course in Common Cartridge archive and reimporting it