Activities Report with My Team filter is showing users not as per the Role Hierarchy

Hi guys, hope you're all well.

As Admin I have made this dynamic Activities report with a filter of 'My Team's Activities' which is not showing the correct roll-up of data as per the Role Hierarchy.

For example, one of the managers in our company has 1 direct report. When opening this report, the manager is seeing not only their direct report, but also users from outside her team.

I've reviewed the Role Hierarchy and it's setup correctly. The other Opportunities based report which use the My Team pre-set filter show up correctly, however for the Activities one, it's showing a mix of users.

Any ideas?