Automatic Litterbox Central

Recently my 7 year old cat has started not going all the way inside the litterbox. I use a Littermaid (have for about 4 years) and every couple of months she goes through these phases where she won't take that extra step into the litterbox and just pees on the receptical (which drains on the floor). I've started to put those puppy pee pads under it to catch anything.

Anyone else have this issue?