Wiktionary
go back to the drawing board
vb. (context idiomatic English) To start again; to scrap a previous idea or plan and try again from the beginning.
Usage examples of "go back to the drawing board".
He would make one pair of lenses, try them out on Bloody Bob, see how well they worked-or didn't work-and then go back to the drawing board.
If the Mole gets stuck before it can complete its mission, Parky and company will have to go back to the drawing board.
They'd go back to the drawing board and then back to 1486 to try the new, improved process on another native.
I imagined someone up there among the medical people was telling the others it was time to go back to the drawing board.