I recently bought this laptop second hand in very good condition, and the only problem I noticed was that the GT 720M GPU downclocks massively when running on AC, to a point where the built-in iGPU runs better. When running on battery the GPU performs as it should do. Here are the specs of the system:
GPU: NVIDIA GeForce GT 720M
The AC adapter is 65W, which is the one that came with the laptop. Could this be the problem? I've seen people sell 90W adapters for this laptop.