Updating source code symbols failing

I'm trying to run the Source code symbols update when launching the Simple Object Designer in BC, but immediately get the error which I have pasted below. Previously (some weeks ago), I've had no trouble running the symbol update process.    ---ERROR--- The record in table Field MetaData Hgd already exists. Identification fields and values: TableNo='85700',No.='1' AL call stack:
"Symbol Management Hgd"(CodeUnit 70310251).ExtractFromFields line 77 - Simple Object Designer by Hougaard
"Symbol Management Hgd"(CodeUnit 70310251).ProcessSymbols line 41 - Simple Object Designer by Hougaard
"Symbol Management Hgd"(CodeUnit 70310251).ImportSymbol line 8 - Simple Object Designer by Hougaard
"Symbol Management Hgd"(CodeUnit 70310251).DownloadAndImportSymbolsFromApp line 38 - Simple Object Designer by Hougaard
"Symbol Management Hgd"(CodeUnit 70310251).DownloadSymbols line 54 - Simple Object Designer by Hougaard
"Object Designer Menu Hgd"(Page 70310263).OnOpenPage(Trigger) line 28 - Simple Object Designer by Hougaard