Lower your dino count settings in single player, and when you load your game do a dino wipe: Cheat destroywilddinos
I play single player a lot. Painted canvases, flags, rugs, and summoned very high level dinos cause lag when too many is placed in a single area. My nephews corrupted my Single Player file for The Center by summoning Negative level dinos (which makes them pretty much almost infinite levels high).