Image caption Sadiq Khan's victory in the London Mayoral election was announced later than planned, on 7 May
The result of last month's London Mayoral election on 5 May was delayed by several hours after staff had to manually query a bug-stricken database.
One of the firms behind the software, DRS, revealed new details of the mishap at the London Assembly on Thursday.
Staff had to collate discrepancies in a spreadsheet, rather than automatically, when tallying final results, said chief executive Steve Gowers.
It was during the late afternoon the day after the election that "discrepancies" in different sets of results were noticed.
A resulting investigation found that the underlying data, the actual numbers of votes in the database, was correct - but the counting software was not reporting it accurately.
Another meeting to discuss what happened will not be held until next month, a spokeswoman for London Elects told the BBC.