Since PLA has such a low melt flow index the dimensional stability is more easily affected by excess heat than other thermoplastics. The picture below shows two 3D Benchy models. Both were printed on with the left extruder of a GB3 version of Gigabot. The one on the left was printed with the bow pointing left and the one on the right was printed with the bow pointed to the right.
Notice the print imperfections on the right hand model. Excess heat can build up on the side of a print opposite the cooling fan. This is especially evident when printing overhangs such as the bow of 3D Benchy. Mitigate such print imperfections by rotating the model for optimal cooling of the overhangs and also by lowering the print temperature