Cant connect to Bitcoin Node on local network

I am running Bisq and also a Bitcoin Core full node. Both are on the same LAN segment (10.x.x.x)

In Bisq, I configured the bitcoin node with its internal LAN address. However it never seems to get connected.
I made sure that I can connect to the node, and with telnet I can reach that port 8333 from the bisq machine.

Here the relevant log snippet:

Dec-30 20:38:25.613 [PeerGroup Thread] INFO  o.b.c.PeerGroup: Attempting connection to []:8333     (0 connected, 1 pending, 1 max) 
Dec-30 20:38:25.617 [NioClientManager] INFO  o.b.n.NioClientManager: Connected to / 
Dec-30 20:38:25.617 [NioClientManager] INFO  o.b.core.Peer: Announcing to / as: /bitcoinj:0.14.4/Bisq:0.6.2/ 
Dec-30 20:38:25.624 [NioClientManager] INFO  o.b.core.Peer: []:8333: Got version=70015, subVer='/Satoshi:0.15.1/', services=0x12, time=2017-12-30 20:38:25, blocks=501766 
Dec-30 20:38:25.624 [NioClientManager] INFO  o.b.core.Peer: []:8333: Peer does not have a copy of the block chain. 
Dec-30 20:38:25.624 [NioClientManager] INFO  o.b.c.PeerGroup: []:8333: Peer died      (0 connected, 0 pending, 1 max) 
Dec-30 20:38:25.625 [PeerGroup Thread] INFO  o.b.c.PeerGroup: Peer discovery took 2.400 ?s and returned 0 items 
Dec-30 20:38:25.625 [PeerGroup Thread] INFO  o.b.c.PeerGroup: Waiting 3375 msec before next connect attempt to []:8333 
Dec-30 20:38:25.626 [NioClientManager] WARN  o.b.c.PeerSocketHandler: []:8333 -  org.bitcoinj.core.ProtocolException: Received AlertMessage before version handshake is complete.

This is repeated on and on.
The node is not running a full blockchain copy (which is correctly detected), I keep only the last 10GB (pruning active).

Any ideas what goes wrong?

Perhaps Bisq needs a full blockchain. It seems like you are not having network issues, so it probably is incompatibility with the node.

Seems your node is in pruned mode or not fully synced.

Peer does not have a copy of the block chain.

Ok, then it should be clarified in FAQ or help texts, that only nodes with the full complete chain can be used (flag “NODE_NETWORK”).
Also, the message “Peer does not have a copy of the block chain.” should be a warning at least, instead of Info.