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Your LimeSurvey version: 6.16
Own server or LimeSurvey hosting: own
Survey theme/template: custom
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The option orce_xmlsettings_for_survey_rendering => true does not work. 
This is from the config.xml:
<container type="buttons" category="Simple options" width="4" title="Survey container" options="on|off" optionlabels="Yes|No">on</container> but the value is always N/A for the container

There is an ticket:  bugs.limesurvey.org/view.php?id=20106 but it is still not working

Are the themes not tested in debug mode? As soon as you set the debug mode to 1 or 2, you can no longer work properly on the theme because there are always PHP errors.