2 USB-Ethernet adapters using the same driver

I have 2 of the same USB-Ethernet adapter that I wish to use on my OpenWrt 18.06.0 r7188-b0b5c64c22 installation on my Raspberry Pi 3 Model B Rev 1.2.

The on-board ethernet adapter is my LAN (br-lan), the first USB-Ethernet adapter (eth1) is my WAN and I want to use the 2nd USB-Ethernet adapter (eth2) for my GUEST network. The LAN is working fine (with DNS, DHCP, Firewall), each LAN client is connected through the 192.168.15.X network. WAN is no issue either, connects flawlessly to my FritzBox modem.

Next, I setup the "guest" interface as 10.0.15.X using eth2 with DHCP and DNS, created the GUEST firewall zone, set the firewall GUEST->WAN as REJECT, ACCEPT, REJECT, created 2 firewall rules to allow the guest network to use the DNS (port 53) and DHCP (67-68) from the Device. This has been discussed in many forums already.

The issue is now that the GUEST network does not connect to e.g. my laptop when plugged in directly. Cable checked, settings checked etc. I'm now thinking that the driver might not be correct. But since this is the very same model of USB-Ethernet adapter, both using the AX88179 driver, it looks like the 2nd (GUEST) adapter is not addressed. Thus the MacBook connected via an ethernet cable does not receive an IP address (DHCP) but in the end sets one of those 169.x.x.x addresses. The network settings panel shows that the cable is plugged in but cannot obtain a connection.

Is there any solution -- other than try to buy a different type of adapter with a different driver and keep your fingers crossed -- to this type of problem?

Many thanks!