Thanks for your reply.
The APs are doing DHCP (for their clients...)
As I see it the fibra-router distributes IPs to the APs (192.168.178.x). They to their clients on a different default (192.168.1.x) subnet.
I did not want to assign fixed IPs to the APs as they are stood in the apartments and...
So yes, I have a fibre-router (in Spain, good service, 600MBit nominal and I will refer to this always as the fibre-router) and I have connected two chains of switches (distances between them are some 20-40 Meters) to two of the ports. Network is set to 192.168.172.x , 254 reserved for lan, only...