It seems that here you are dealing with a SQL problem down at the Oracle data source level and Denodo is just reporting the error. What I would do to try tracking this is to go to the [Execution Trace](https://community.denodo.com/docs/html/browse/7.0/vdp/administration/appendix/execution_trace_information/execution_trace_information) and at the lowest level click on the data source node. On the right I would be able to see the SQL sentence that Denodo is executing at the Data Source. I would then use this query to work directly in the data source and try to identify the column that gives trouble.
This is an SQL error reporting from your Oracle data source. Denodo in this case is just retrieving that error and showing it to you.
Hope this helps!