I would suspect the constant moving inside and outside did this. The TV's are getting lighter and lighter which means the plastic on the back and around the TV is getting thinner and thinner, thus its bending as you pick it up and bring it in. I would imagine this would happen overtime with almost any indoor rated TV in an outdoor setting. I'm not sure where you are located but the outdoor temps and humidity may also pose issues as it could weaken the plastic over time in addition to if the wind is causing the TV to move back and forth further bending it enough to crack it...but that's just a guess. When you are picking it up to move it are you picking it up by the tripod or the TV itself? Its possible if your picking it up by the tripod that's whats causing it to bend as well and would suggest picking it up by the TV itself. Another suggestion may be to beef up the TV mount where it connects to the TV by possibly using some metal to create a square box so it doesn't bend the plastic backing. All just a few guesses. Outdoor TV's are expensive so I understand the idea of using a lower cost indoor one (I am sure someone will be critical and say you should never use one outdoors), but is it possible you can build a box that it could go in permanently with some vents to allow heat to dissipate?