Even with my considerably weaker Radeon 680M, or even on my previous laptop which had a weaker-again GTX 960M, I noticed this too (I get that you might expect it to happen less on a weaker GPU, but Loap has had a surprising number of issues that only occur with unlimited frame rates and get worse on stronger hardware). I'm not really sure why it happens, but it is something I want to fix at some point.