Help with footstep box triggers within another box trigger.

Hi there, I am a sound designer and I am working on a project that involves using Unity and Wwise audio middleware, so my programming skills are very basic. My project is a first-person VR experience where the user is able to explore a small outdoor area with a couple of houses that can be explored inside. Footstep sounds are triggered via events in the avatars animation and change of terrain/surface sounds are triggered as the avatar enters a box collider (set as trigger) with a script attached for unity to communicate with Wwise and let it know that the surface has changed and to set a switch to play the appropriate footstep sounds.

My issue is, I have placed one of these box triggers to cover a large house ,as the house has wooden floors, but there are carpets/rugs inside that require a different sound to be played. Smaller box triggers within the large house trigger are used to cover these rugs, but when I test the game they only trigger on occasion (i.e one moment it'll switch between wood to rug sounds but other times it'll only play wood sounds regardless of walking on rugs or not).

I apologize if my explanation is not clear enough but if someone could perhaps help, I will gladly explain things further along with script information.