My first machine was a Delonghi and I would have that happen to me too. In some ways, it could be a matter of the design of the basket.Hmm, my machine came with a thing called "the razor" which is supposedly to trim the puck down to the correct level. After tamping, the level of the coffee is alway well below the reach of the razor.
You are probably right that it is too much coffee and that it expands during infusion.
The combination of the two points above must mean that I'm tamping with too much force. The infusion pressure does get pretty high to be fair.
So, I'll try a bit less coffee, maybe a slightly finer grind and lower tamping force.
Lots of parameters to tweak - I can see the parallel with hifi!
Currently, my puck does not touch the shower screen until after extraction: it does not stick however.
How much are you dosing? Is there any instruction about max dose for your basket?