Out of interest, how old is the machine and how long since you completed a descale before this one? It may be that there is a reasonable build-up of scale in the boiler if its been a while. Such being the case, it might pay to try another descale session with maybe a slightly longer period with the solution sitting in the Boiler and another good flush-through afterwards.
If youre using filtered water then this wont count but if not, is there any reason to believe that there may be sediment coming though from your main water supply? If not, a decent water filter would definitely be worth while; either an inline type that you can leave immersed in Silvias water tank; an under sink system feeding a faucet that you source the water from; or a Brita water filter jug with a filter cartridge that you change regularly.
Hope theres something of use to you there.... :)