Time and Labor not preventing EEs from taking leave time they don't have

9.2.45 PT 8.59.15 T&L

As an example, an EE has 30 hours of vacation. They take the 30 hours this week, and their balance reduces to 0. Next week, with their balance already at 0, they enter another 30 hours, but the system still allows them to take it. Has anyone else experienced this? It should be preventing them, but it is not, and they are going negative if it isn't caught manually.