ETL Module Execution failed, cannot insert duplicate key row in object

Question

The following error message occurs in my Operations Manager event-log after following the instruction for reimport previously removed mp:

ETL Module Execution failed:  
 ETL process type: Load  
 Batch ID: 652958  
 Module name: LoadOMDWDataMartCustom_ClassDim  
 Message: Cannot insert duplicate key row in object 'dbo.Custom_ClassDim' with unique index 'UniqueIndex'. The duplicate key value is (34ff07e4-10c8-fb97-3284-5c7747f41894, cbbf64bf-154c-0f3c-1765-8792bcd0c992).  
The statement has been terminated.  

And I got the same error msg for CMDWDataMart. I checked OMDWDataMart and CMDWDataMart for the record:

SELECT Custom_ClassDimKey, [BaseManagedEntityId], Id FROM [OMDWDataMart].[dbo].[Custom_ClassDim]  
where  [BaseManagedEntityId] in ('34ff07e4-10c8-fb97-3284-5c7747f41894', 'cbbf64bf-154c-0f3c-1765-8792bcd0c992')  

Custom_ClassDimKey         BaseManagedEntityId                        Id  
47                        CBBF64BF-154C-0F3C-1765-8792BCD0C992        SR62184  

And I query DWRepository for the record:

Custom_ClassDimKey         BaseManagedEntityId                        Id  
1                         CBBF64BF-154C-0F3C-1765-8792BCD0C992      SR62184  

The difference is the value of Custom_ClassDimKey. Can I solve this issue by deleting the record in the:

1) [OMDWDataMart].[dbo].[Custom_ClassDim] and [CMDWDataMart].[dbo].[Custom_ClassDim] or
2) [DWRepository].[dbo].[Custom_ClassWebDim] or
3) [DWRepository].[dbo].[Custom_ClassDim], [OMDWDataMart].[dbo].[Custom_ClassDim] and [CMDWDataMart].[dbo].[Custom_ClassDim]?

4) or neither nor

I found a similar issue reported here.