My friend's daughter did this, too, except she'd been potty trained for much longer. As my friend was talking to me about it, I had an insight that hopefully was useful.
I know that in my life, when I learn something new, at first I have to put a lot of effort into learning it and doing it. But after a while, I want to not put so much energy into it. So I try to put it on "auto." And that's when I get a little "sloppy" and make some mistakes.
When kids are learning to walk, it's very deliberate. They try very hard not to fall. But after a while, they start to put it on "auto," trying to walk without having to think about it so much. They try to be able to walk and look at things at the same time. That's when they don't see the step or the toy and they trip. But they learn and keep trying to put it on auto until walking is second nature.
When I try a new recipe, I read the instructions carefully, and then end up reading them several times while I'm cooking, to make sure I'm doing it right. But my 3rd or 4th time, I'm usually in a hurry and I try to cook it without spending as much effort on it. I usually make a few mistakes, but the next time I make less, and so on, until I'm good at making that recipe quickly.
So hopefully, your daughter is trying to put her potty training on "auto." She doesn't want to have to spend the rest of her life asking herself, "do I need to go potty right now?" So she's trying to play and not think about going potty while still recognizing that she needs to go. She's bound to make mistakes.
If that's what's going on, you may have to remind her to think about it every so often.
Another thought is that sometimes kids don't want to pull themselves away from their toys. Now that she's confident in her potty abilities, she may get the feeling she needs to go, but thinks, "I'll go in a minute, because I don't want to stop playing," and then she can't hold it.
Maybe that's not it at all, but I thought I'd throw that out there.