No connection to storage node via internet?

Hi, I am trying to set up deduplicated backups via internet to my storagenode-server.

When setting up a new backup job in Acronis B&R 11.5.37975, it connects fine to my storage node and vault via LAN.

When I try to connect from outside via my public ip (have opened TCP/UDP port 9876 in firewall), I get to enter my credentials, and the node shows up under "Storage Nodes".
When I click the small arrow next to the storage node (to see available vaults), all I get is "Loading".
On the Storage Node Server, the Centralized vault in question, hangs (Vaults -> Centralized).
Choosing the vault and clicking "Refresh" produces a constant "Loading" under the tab "Free space".
Only way to reset to normal (so I can connect via LAN) is to restart the Acronis Storage node Service.

How can I solve this?

Thanks.