Litter Robot III - Open Air version

I'm wondering if anyone has had this issue and has found a resolution?

We own a Classic Litter Robot and have for a few years. Both cats were using it fine until one decided to poop outside it about 2 months ago. We put out a regular pan and that fixed it so we thought maybe we needed two boxes instead of one. Although they seem to prefer the pan to the LR regardless. I wonder if it's the safety in the openess of it.

We decided to buy the new LR III - Open Air and just got it set up in a different room. Unfortunately my husband took away the old litter pan too fast so I've had to put it back. But one cat used the old LR right away and the other cat peed in the old LR, but again, pooped outside.

I've heard of people having this issue of cats not wanting to poop in the LR. Wondering how you conquered that, if you did. Thanks for a response.

I have not used this box.  Does the box make different sounds from the others?  

We have had 2 LitterMaid boxes.  When the first broke we got another and it sounded very different!  Fortunately the cats weren't bothered; but every time it went off when we had company here, people would stop mid sentence trying to figure out what the noise was.    That came to mind when I was reading your question.