Thanks for pointing me in a direction @kid63 . 1.3.1 is not listed here: I only found it here: https://support.omadanetworks.com/en/document/108306/?app=wifi-toolkit But with no download link.

The load balancing between two internet connections does not seem to be according to the bandwidth ratio. WAN1 with 175 MBit/s up and 40 MBit/s down WAN3 with 100 MBit/s up and 40 MBit/s down Load...