I just posted this to Neko but will just paste it here as well in the hopes that it makes some sort of noticeable change.
I'm looking at the itch build as we speak and am unable to replicate the issue as of yet. I'll keep posting suggestions though in the hope that one of these things may correct whatever issue is occurring.
Do you have Vsync enabled inside your Graphics Card Dashboard/Settings? If so, could you try disabling it? I noticed that having it enabled drops the FPS noticeably for me.