Delonghi Prima Donna exclusive coffee pods break up ?

The Delonghi Prima Donna exclusive that I have is 4 years old. We only use it on weekends to make morning cappuccinos, not daily use. It makes a good cup of cappuccino, the coffee runs out smoothly, and its automatically made steamed milk is nice and thick and frothy. When I open the machine to clean it, the pods that are created sometimes are in the drip tray correctly and are fully formed pods. However, sometimes, the pods have broken up and there's coffee spilled all over the inside. I have to really clean it well and vacuum it with a very small vacuum to get all the coffee grounds out. The coffee pods are not well formed and have broken up, which causes the coffee grinds all over in inside of the machine. I only use whole beans, I have never used ground coffee in the machine. I also clean the infuser by soaking in water once a month, and I also descale when the machine tells me to. Why do you think the coffee pods that are created are falling apart sometimes and sometimes they stay as whole pods and fall into the drip tray where they are supposed to go. And sometimes they do not? Thanks.