It turned out there were some things which required immediate fixing. The two expanders has their main connector inverted on the PCB! Of course, there is a way around, but it is much cleaner to have it in the right way.
The main board had some header holes too small. I must have changed those by mistake since they were fine in the previous version of the board. Anyway, fixed those too. Also, the crystal frequency is (finally!) set at 18.432 MHz.
All is fixed now and updated on the website.