ok everyday i have the same problem. i was talking to my friend and i think i figured it out!
here's the problem. my ds1 won't take a nap. then he is tired as crap and acts crazy. i was doing quiet time at the time i think he should nap, but he never does. now i'm saving quiet time for when he is just so tired he can't behave (around 4pm). that way the kids are separated. after quiet time, it will be time for dinner and bed. so far it is going much better today.