Have you ever seen hairline cracks in the reservoir of the Towergarden? I was cleaning my unit out and saw a hairline crack line about 2 ft long! i have photos!
The only cracked unit I have seen was after a tree fell on it. Sorry! I would contact Tower Garden.
I have one in mine. Check the support that your TG sits on. If it irregular or has any ridges, once the tub is filled, these may cause stress in the plastic. Just a thought.