Game crashing when joining friend on local server

Hi,

We play with 2 PCs in one local Network (one router).
Until recently this worked perfectly.

Now my friends game keeps crashing when he tries to connect to our game. He can still start new games etc. without Problems but Starbound crashes as soon as he is trying to join my game.

We already tried
- deleting Player and universe files
- verify game files in steam
- create a new character
without success.

I´m posting the log below, any idea what is wrong here?
Way down the log there is a...

Game crashing when joining friend on local server