Limit number of attemps field disapears while integrating a QTI 2.1 test

If you integrate a QTI 2.1 test into a existing preconfigured Testbaustein, where e.g. the number of attempts is limited to 1, the limitation field disappears... simultaneously the option "Limit number of attemps" stays visible.
nevertheless the limitation works well.
it is possible to re-choose the option to make the field visible and set a number but whenever you publish or reopen the test, the field is gone.