Cannot load status: no model for token={token}

[vcutrona]

When taking the Live demo survey with AQ version v1.6.7, we experienced the following error:

2024-05-16 07:33:39.171 INFO  ch.idsia.adaptive.backend.controller.SurveyController            User with token=65c32627-6619-4fa0-80f0-e4b55be4dfaa has ended with a finished survey
2024-05-16 07:33:39.252 INFO  ch.idsia.adaptive.backend.controller.SurveyController            User with token=65c32627-6619-4fa0-80f0-e4b55be4dfaa request the results
2024-05-16 07:33:40.004 INFO  ch.idsia.adaptive.backend.controller.SurveyController            Request all answers for token=65c32627-6619-4fa0-80f0-e4b55be4dfaa
2024-05-16 07:34:14.030 INFO  ch.idsia.adaptive.backend.controller.SurveyController            User with token=65c32627-6619-4fa0-80f0-e4b55be4dfaa gave answers=[90]
2024-05-16 07:34:14.500 ERROR ch.idsia.adaptive.backend.controller.DemoController              Cannot check answer for token=65c32627-6619-4fa0-80f0-e4b55be4dfaa, questionId=9, answerId=null, statusCode=400 BAD_REQUEST
2024-05-16 07:34:14.501 INFO  ch.idsia.adaptive.backend.controller.SurveyController            Request status for token=65c32627-6619-4fa0-80f0-e4b55be4dfaa
2024-05-16 07:34:15.232 INFO  ch.idsia.adaptive.backend.controller.SurveyController            User with token=65c32627-6619-4fa0-80f0-e4b55be4dfaa request a new question
2024-05-16 07:34:15.614 ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet] Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentExcep>
java.lang.IllegalArgumentException: Cannot load status: no model for token=65c32627-6619-4fa0-80f0-e4b55be4dfaa
       at ch.idsia.adaptive.backend.services.SurveyManagerService.lambda$getSurvey$1(SurveyManagerService.java:104)
       at java.base/java.util.Optional.orElseThrow(Optional.java:403)
       at ch.idsia.adaptive.backend.services.SurveyManagerService.getSurvey(SurveyManagerService.java:104)
       at ch.idsia.adaptive.backend.services.SurveyManagerService.isFinished(SurveyManagerService.java:112)
       at ch.idsia.adaptive.backend.controller.SurveyController.nextQuestion(SurveyController.java:334)

It seems the error occurs right after the user completes the survey.
More details are available in this issue.
I attach the complete log from our running instance for your convenience.