Not sure if this is the same bug (Windows 10), but I get similar lag after a certain length into the game. There will be lag spikes every second or so where the game micro-freezes, then resumes. It's like a framerate jitter. It appears to be worse when I have in-game menus open, but persists regardless. Zoom level has no affect, so presumably it's not an on-screen complexity issue.
But the issue vanishes when I play in windowed mode. Same resolution but not full-screen and the lag spikes disappear. Game runs perfectly smooth in windowed mode.