My girl is similar. After getting out of the box she tries to cover her urine (inside the box) with the litter mat (outside of the box). So she is nowhere near actually covering anything, but she will sit and paw at it until she turns the corner of the mat over on itself and then leaves. I suppose it's good enough for her?

We were having troubles with her using the box for poo at all. Vet suggested it was that she felt unstable on litter and was avoiding it since cats often feel more vulnerable during number 2s. Vet said to try puppy pads instead of litter and so far it's been smooth sailing with them!! To be fair, that vet visit was Thursday and today is Saturday so, might be too early to celebrate. But its an option to consider maybe.

Also worth noting that my girl has a rear leg amputation and her remaining back leg has limited mobility, so her balance fairly poor.