Dualit, known as the last word in toasters, are probably one of the best known British manufacturers of domestic machinery along with Dyson. Once my cheap De’Longhi machine started to give up the ghost, then, I thought that it made sense to get one from Dualit. It did, but there was one issue which had me scratching my head for a bit.
The Dualit Espress-auto 4 in 1 Coffee and Tea Machine works well but can have trouble if too much pressure is required and this does not seem to be covered in the instructions or other support documentation.
As is the norm for domestic coffee machines, and understandably given they cost 1/10th of the price of their commercial equivalents, they do not generate vast amounts of pressure. Relatedly, if you tamp the coffee too much so it is too tightly packed in the cassette you will increase the pressure required to pump water through the cassette and the machine may not manage it.
Further increasing the pressure required to dispense coffee are the recommended filters. The filters are recommended to make sure that the holes do not get blocked.
When the machine cannot generate high enough pressure it will start to dispense, then give up almost instantaneously, with flashing button lights. This is confusing if you do not know what is happening, because the lights flashing usually means that the heating system, or thermoblock, as Dualit like to call it, is not yet up to temperature.
Source: Cameron et al., Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment, Matter (2019), https://doi.org/10.1016/j.matt.2019.12.019
The fix, as I later found out, is to simply use more porous filters. I have been using AeroPress filters (‘AeroPress Micro-Filters’) from California which seem to allow greater flow — since using these I have not had any issues.