Employee is still showing as incumbent in Position Hierarchy

Hello experts,

we have this employee who's previous position is 30997, but now, this employee is now in different position.

In position 30997, there is no longer any current incumbent.

However, when looking at the HCM Position Hierarchy, this employee is still shown as the incumbent.

what is the reason of this? and pls provide a solution to solve it.

regards,

Maria