Steps:
Wnen I enter a ship, switch to Build Mode, and press the left-<CTRL> key, the game kicks completely out (multiplayer mode).
I tried remapping the Advanced Build Mode to the <TAB> key. The <CTRL> key no longer kills the game, but the <TAB> key does, so it's somehow tied to invoking Advanced Build Mode.
Never happened before I upgraded to v0.19498.
Reproducible. Tried this many times.
Updated version of Java. Still occurs.
Rebooted box. Still occurs.
Tried fresh StarMade install instead of upgrade. Still occurs.
Tried using a fresh server world. Still occurs.