One thing that I would take into account is that when you’re busy, the interior temperature if your grinder starts increasing, which will cause your espresso to start straying from what you dialed it to do. Also, if you’re not weighing your dose and yield, it’s very hard to achieve consistency in a high-volume shop, so that would be your first problem. Assuming you are weighing your shots, simply write down the dose , yield, & time of the shots for each bean when you initially dial in, and when you see the time start to sway due to temp change in the grinder, it’s much easier to make minor adjustments in the middle of a busy flow when you know what to aim for. (I.e. If my single origin was pulling 20 in & 45 out, with a time of 27-29 seconds, and in the middle of a rush I notice the espresso starting to pull the same dose/yield in 23-25 seconds, I know I just need to go finer by a degree or two, and can make the adjustments in between drinks. But yeah if you’re not weighing the shots, that’s definitely step one for attaining ideal consistency.
Hope this helps!