Recently, while activating a Business Process Flow, we got below error: “An attribute with the specified name already exists. Exception Message: Column names in each table must be unique. Column name ‘stageid’ in table ‘EntityName’ is specified more than once.”
While checking the entity metadata for which we had created BPF, we found that Business Process Flows was unchecked. After ticking the checkbox, we saved the entity and published it.
Then, we tried to activate the BPF again and it worked.
Hope it helps !!