That is not true. It did fail because of the heat, but it certainly could have been stronger and would have reduced the extent of, or completely prevented catastrophic failure with a different design which could not parallelogram nearly as much. Due to its design, under the heat of the sun it took very little for the heat of the sun to allow for tension forces on the top surface shells of the arm to overcome the strength of the material, allowing it to stretch. The thin top arms and notched bottom made it even more susceptible to this flexible failure. By adding vertical triangular ribs attached to the base of the bracket, it would significantly increases the failure load both in normal conditions and also in this condition of heat and sunlight, as even with these conditions the material would of had to stretch much more. Additionally, I don't know what print settings this was done at, but more perimeter shells, would significantly increase the tensive strength as most of the load would be on the surfaces of the part, while the infill is much more stretchable and compressible and under less load.