This is the log for the process of opening both connections, where 172.18.174.34 is the problematic server and 10.112.83.248 is the working one:
2015-12-03 15:36:12.794 - DBeaver Enterprise 3.5.4 is starting
2015-12-03 15:36:12.795 - Install path: 'file:/C:/Program Files/DBeaver/'
2015-12-03 15:36:12.796 - Instance path: 'file:/C:/Users/Joao Pio/.dbeaver/'
2015-12-03 15:36:15.260 - Initializing DBeaver Enterprise 3.5.4
2015-12-03 15:36:15.261 - Host plugin: com.jkiss.dbeaver.ent.application 3.5.4
2015-12-03 15:36:15.261 - Initialize Core...
2015-12-03 15:36:15.593 - Opening QMDB connection...
2015-12-03 15:36:15.930 - QMDB started
2015-12-03 15:36:15.931 - Core initialized (670ms)
2015-12-03 15:36:17.286 - MONGO INFO: Cluster created with settings {hosts=[172.18.174.34:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500, description='DBeaver Enterprise 3.5.4'}
2015-12-03 15:36:17.368 - MONGO INFO: No server chosen by ReadPreferenceServerSelector{readPreference=primary} from cluster description ClusterDescription{type=UNKNOWN, connectionMode=SINGLE, all=[ServerDescription{address=172.18.174.34:27017, type=UNKNOWN, state=CONNECTING}]}. Waiting for 30000 ms before timing out
2015-12-03 15:36:18.850 - MONGO INFO: Opened connection [connectionId{localValue:1, serverValue:523115}] to 172.18.174.34:27017
2015-12-03 15:36:19.219 - MONGO INFO: Monitor thread successfully connected to server with description ServerDescription{address=172.18.174.34:27017, type=STANDALONE, state=CONNECTED, ok=true, version=ServerVersion{versionList=[2, 4, 12]}, minWireVersion=0, maxWireVersion=0, electionId=null, maxDocumentSize=16777216, roundTripTimeNanos=362620727}
2015-12-03 15:36:20.679 - MONGO INFO: Opened connection [connectionId{localValue:2, serverValue:523116}] to 172.18.174.34:27017
2015-12-03 15:36:34.819 - MONGO INFO: Cluster created with settings {hosts=[10.112.83.248:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500, description='DBeaver Enterprise 3.5.4'}
2015-12-03 15:36:34.822 - MONGO INFO: No server chosen by ReadPreferenceServerSelector{readPreference=primary} from cluster description ClusterDescription{type=UNKNOWN, connectionMode=SINGLE, all=[ServerDescription{address=10.112.83.248:27017, type=UNKNOWN, state=CONNECTING}]}. Waiting for 30000 ms before timing out
2015-12-03 15:36:34.938 - MONGO INFO: Opened connection [connectionId{localValue:3, serverValue:2158}] to 10.112.83.248:27017
2015-12-03 15:36:34.964 - MONGO INFO: Monitor thread successfully connected to server with description ServerDescription{address=10.112.83.248:27017, type=STANDALONE, state=CONNECTED, ok=true, version=ServerVersion{versionList=[2, 4, 8]}, minWireVersion=0, maxWireVersion=0, electionId=null, maxDocumentSize=16777216, roundTripTimeNanos=23205288}
2015-12-03 15:36:35.063 - MONGO INFO: Opened connection [connectionId{localValue:4, serverValue:2159}] to 10.112.83.248:27017
This is a screenshot of what both databases show me in the UI:

- mongo.JPG (106.32 KiB) Viewed 17058 times