Now I am not sure whether it was the Firewall allow rule at the client side, or the Range Mapping rule at the server side.
Client side Firewall rule:
Source IP: 192.168.1.3
Source Port: <not set>
Destination IP: nl4.probackup.nl
Destination Port: 4382-4385
Server side Range Mapping rule:
Service Ports: 4382-4385
Map to Ports: 4282-4285
Inbound IP Address(es): All selected
Included Server(s): 1 selected, Weight 1
After changing the Range Mapping rule to several Port Mapping rules, the connections were established.