DNS Issues?

I’ve got two virtualmin servers, each at seperate locations. I’ve got 5 domains hosted on server1 and 2 domains hosted on server2. I’ve set (as far as I can tell) both servers to function as the master DNS zone for the domains hosted on them, and as a slave dns zone for the domains hosted on the opposite machine. My problem is this.

I added a domain to server2, and all the dns works, and from what I can tell propagates correctly to server1
however, when i add a domain to server1, only a blank zone file is sent over to server2. And having left this for several hours, and even done a forced rndc update I can’t seem to get the zone files to send from server1 to server2. Any ideas where to even start troubleshooting?