Please test with your Brisbane no. NO issues. Have checked all port forwarding and the 3CX tests come up ok. But that doesn't necessarily means its ok!! IF you need some changes to our NATTING please advise and will do.
I noticed that the Cisco phone 401 has been setup as a 3cx client. Although I have made this work with the 504g before. I think it best if it was provisioned as a 504g. I am familiar with this model but not he polycoms and linksys models. so You may want to provision them correctly as well.