Only when I apply 230V to the contacts, even without load, I can see the spikes. You can say that I switch 3cm of pcb tracks on and off.

If I understand you uou have the following

220VAC --- relay cxontact -- 3 cm PCB trace  -- nothing.

If that is correct, try the following
1) apply the 220VAC to the other side of the contact.
2) apply the 220VAC to both sides of the contact.

Let me know what happens.

Erik