Was the lam fastened with contact glue" Were the seams butted and glued properly? For water to get into a properly butted seam is to me hard to understand.
But in direct answer to your post, particle board once contaminated will and cannot be fixed. I hate particle board of any kind and it should Never be used where water is around.
In my opinion, you do have a problem and fixing it is only going to be removing all and replacing the contaminated particle board. Next time use ply wood.
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