Multiple Trunk setup won't register

Our VoIP provider sends us calls from 1 of 11 IP addresses. In order that these are recognised by the FreePBX system we configured a trunk for each host address. In FreePBX 2.11 this worked fine and all trunks registered. However, in FreePBX12 none of the trunks would registered. We only got one trunk to register by disabling the other 10.

Any suggestions as to why this worked in one FreePBX instance but not the other?