Navigating custom (somewhat complicated?) ComboBox drop down area issues

There is A LOT of code that I used to construct this guy but this is really the relevant breakdown of the elements inside the pop-up (including the pop-up).

The issue is how it navigates when using arrow keys...

Let's say I've tabbed into the control. I have it set so that it goes directly into a checkbox, bypassing the comboboxitem. However when I press a direction, weird things are abound.

(I have no clue what the names of the controls are since it is done programatically so these are placeholders)

It just stays within those 3 custom checkboxes even though I have 48 of them. I am filling the items via the codebehind if that makes any difference

If you need any clarification or even code snips let me know.

Thanks!