frame skipping

I'm experiencing severe frame rate drops, particularly in challenge mode, but generally once I pass the second star mark on any island or once my parks fill up with assets and AI. It usually returns to normal once I delete all my buildings and sell all my dinosaurs and/or there are no guests...

Finally, I have video proof of these horrible frame-skips / lag spikes. Many people, including myself, have tolerated these for a long time, and I certainly noticed them as soon as I started playing the game several months ago. But they were never quite as bad or frequent before the new April...