Not able to add extension field to Data Source

Hello,

I'm trying to add an extension field from Service Request BO to the data source Ticket (CRMSRQHB). But it gives message saying "Retrieving data sources failed Metadata utility: could not find field Y1IUIUVXY_F0000BE39758393A".

If I try to add other fields, it gives the same error with different field names. Any help would be appreciated.

Thanks.

Regards,

MB