LitterBox help?

S

So we have two cats and they use their litter boxes and everything but the problem is that no matter what kind of box or litter we use THEY WONT LEAVE THE DAMN THING ALONE.

We have one that if its freshly cleaned sits in the dang thing like it's a cat bed/guarding it. And the other will just scratch in the litter or the side of the box forever. Like anywhere from normal amount to 30 minutes. And not just after using it, sometimes she will just walk up to it and start pawing at it. Doesnt matter if its clean or dirty. Usually if you snap your finger or click your tongue she'll stop.

We moved and havent found a new vet yet. They are both healthy and seem happy despite there being a baby and a dog in the house now. They've done this for as long as I can think of but hasn't really been an issue till we moved here because no matter where we put the boxes its loud enough it wakes up the baby (loft style town house).

The previous vet said they were healthy not to worry about it but I just dont know what to do at this point.

*both are adult female cats, fixed, their claws are intact, and they were moth rescues from abuse and/or abandonment.