The lattes served today tasted inconsistently sour and bitter. How can I check if the grinder has drifted?

Customers during the morning shift at the coffee shop reported that the latte flavor was inconsistent today—the first cup was too sour, and subsequent ones were too bitter. The beans and milk hadn't changed. I first recorded the shot time, dose, yield, and water temperature, and discovered that the grinder setting had been micro-adjusted by different staff members during the rush, and the recipe…