Yes! We're in the same boat at the moment. Our DS1 didn't have an issue with poos on the potty and then toilet, but DS2 just won't go poo on either. He waits until he's in a pull up for a sleep, before going. So frustrating. We've also had quite a few accidents in his pants. I'm not sure what to suggest, as we didn't go through this with our first son. We've got a sticker chart next to the toilet (as he got a bit lazy with his wees) and not sure what else to try. We're trying not to get angry when he has accidents and talk about his big brother doing poos on the toilet. He got to the point where he started regressing and didn't want to wee on the toilet, so he's now doing 'big boy, stand up wees'. Still no poos yet.
Sorry I'm not able to offer any suggestions. I guess they won't be doing number 2's in their pants when they're 21!