Bonita Error: be_TRT_2 Exception

We are using Bonita Open Solution version 5.6 and we are getting the following exception:

WARNING: Activity will be put in the state FAILED due to: org.ow2.bonita.facade.exception.BonitaWrapperException: org.ow2.bonita.facade.exception.RoleMapperInvocationException: Bonita Error: be_TRT_2Exception caught while executing role mapper: org.ow2.bonita.facade.def.InternalConnectorDefinition@556eafa6

Can anyone offer some help on how I could trace or solve this problem?