Set the Standard
Different team members may have varying responsibilities, schedules, and goals, but they must all adhere to a common standard. A level of productivity and trustworthiness is necessary to function. Failure to meet that standard should be met with correction.
The standard must be clear and consistent. Teams who see fellow members failing to meet the standard over and over will question their own efforts. If so-and-so gets away with that, why can't I?
As a leader, there must be candid and precise answers as to why a certain team member isn't required to meet the same standard. And those cases should be few, far between, and temporary. It can be difficult and awkward to address someone not meeting the standard, but in these cases the integrity of the team takes priority.