Checkbox checked and unchecked events are being fired when I select an expander

I just noticed this issue, whenever I select an expander whose parent is a checkbox it triggers the checked/unchecked events even though the checkbox is not checked.

Here is a .gif that shows it occurring. The number in the upper right represents the number of checkboxes checked, I set to to just count up and down whenever a box is checked or unchecked. The counter itself is not the worry here though, just a way to show it happening.

For each checkbox their Checked and UnChecked events point to a method of my choosing.

What is causing this to happen, and how do I go about preventing it?