So far we didn't have any more poop in the crate incidents. When we need to leave the house during the day, we leave Trezzi's crate open in the fenced off area in the kitchen. He knows where the pad is and goes there. He hasn't had accidents so far when he's in the kitchen.
We lock up Lulu in her crate though — she learned how to jump the fence

, and does it every time now if she is left in that area to her own devices.
I was more worried about nighttime because he sleeps in his crate, closed-off in our bedroom. I am not sure what happened that night when he pooped in his crate, but it hasn't happened ever since. I am very happy about it.
I also limit their last feeding time to 7 pm. We usually go to sleep around midnight, and the monkeys hangout with us till then; so they have plenty of opportunities to go if they need it. And then hubby wakes up around 5 am to take Trezzi to his pad in the kitchen, just in case he needs to go.