hi, i'm creating a bpmn diagram (a process definition ) using JBPM 5 web process designer.

when i draw a business task and go to FILE ----> SAVE CHANGES  , it will save it with no problem

but when i go to the task's properties and add something in DataInputSet property , it won't save and

says:

Unable to perform user action due to error(s).

Validate your process before saving, and view server logs to see error details.

i have attached my server log .

thank you so much!