Business Central unable to authorize a user for claiming/starting a task assigned to a role, using database login module

Issue

• BPMS 6.1.0 installation has been configured to use a custom database login module (with a table of roles and their mapped users listed) to authorize users belonging to a group/role for claiming/starting tasks. However, for the following scenario it does not seem to work properly.
  e.g. There is a task that can be executed by Role1 role.

1. Login to business-central using a user user1 which is not mapped to this role Role1
2. Add the role to the user user1
3. try to claim or star the task (e.g. via REST)

This throws the following exception.

Caused by: org.jbpm.services.task.exception.PermissionDeniedException: User '[UserImpl:'15426']' does not have permissions to execute operation 'Claim' on task id 425
    at org.jbpm.services.task.internals.lifecycle.MVELLifeCycleManager.evalCommand(MVELLifeCycleManager.java:104) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.internals.lifecycle.MVELLifeCycleManager.taskOperation(MVELLifeCycleManager.java:341) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.impl.TaskInstanceServiceImpl.claim(TaskInstanceServiceImpl.java:119) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.commands.ClaimTaskCommand.execute(ClaimTaskCommand.java:52) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.commands.ClaimTaskCommand.execute(ClaimTaskCommand.java:33) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.commands.TaskCommandExecutorImpl$SelfExecutionCommandService.execute(TaskCommandExecutorImpl.java:65) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.drools.core.command.impl.AbstractInterceptor.executeNext(AbstractInterceptor.java:41) [drools-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.persistence.TaskTransactionInterceptor.execute(TaskTransactionInterceptor.java:54) [jbpm-human-task-jpa-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.drools.core.command.impl.AbstractInterceptor.executeNext(AbstractInterceptor.java:41) [drools-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.drools.persistence.jta.TransactionLockInterceptor.execute(TransactionLockInterceptor.java:67) [drools-persistence-jpa-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.commands.TaskCommandExecutorImpl.execute(TaskCommandExecutorImpl.java:40) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.task.impl.command.CommandBasedTaskService.execute(CommandBasedTaskService.java:139) [jbpm-human-task-core-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.kie.services.impl.UserTaskServiceImpl.execute(UserTaskServiceImpl.java:921) [jbpm-kie-services-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.services.cdi.impl.UserTaskServiceCDIImpl$Proxy$_$$_WeldClientProxy.execute(UserTaskServiceCDIImpl$Proxy$_$$_WeldClientProxy.java) [jbpm-services-cdi-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.kie.remote.services.cdi.ProcessRequestBean.doTaskOperation(ProcessRequestBean.java:315) [kie-remote-services-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    ... 55 more

• How to solve this kind of problem?