Sorry you're dealing with that. If your store is exactly the right amount of busy the rotation is forced and frequent. There's no one up front so tech A running pickup/drop-off answers the phone. Someone comes up to the counter while they're on the phone so drive thru tech B goes up and helps them. Tech A gets off the phone and helps the customer that has just pulled up to the drive thru. The phone rings, the person filling tech C goes to answer it. The person tech A is helping in the drive thru is having am urgent situation so tech A puts it in critical and fills it. Tech B is taking awhile troubleshooting some billing issues so tech C goes up to help with the line. Etc etc.

A strict rotation schedule can hinder you as much as help you. It really comes down to the team culture and if people are eager to help their coworkers or not. But when things are as bad as they are for your pharmacy it might be time to enforce a schedule :(