Random short-answer matching just does not work

Random short-answer matching just does not work in 2.1 and 2.2.
1.- It seems that some strings are missing from quiz lang file (i.e. randomsamatch, randomsamatchnumber etc.) which throws an error when editing the question.

Invalid get_string() identifier: 'randomsamatchnumber' or component 'quiz'

2.- Even when question has been created, it's impossible to use it :
Coding error detected,
Stack trace:

line 234 of \question\engine\bank.php: coding_exception thrown
line 673 of \question\type\questiontypebase.php: call to question_bank::load_question_definition_classes()
line 660 of \question\type\questiontypebase.php: call to question_type->make_question_instance()
line 275 of \question\engine\bank.php: call to question_type->make_question()
line 265 of \question\engine\bank.php: call to question_bank::make_question()
line 39 of \question\preview.php: call to question_bank::load_question()