It is Never a good idea to store wooden objects inside your crawl space. Check out the Video showing termites inside a newer home in a wooden pallet
Plexi vents were installed in a lot of homes but most have been replaced and they are sold under a lot of different names plex-vent and terms similar to this are the most common. They are a very thing plastic and can fail, one of the common things to identify them is the funnel with the tube running out. These should be replaced when found.
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