Saving or deleting subassemblies while connected to a server freezes the game (all buttons unresponsive, camera still works). When not connected to a server works fine, removing all other mods did not fix, 1.5.6.

Log when trying to delete a subassembly:

[LOG 04:01:14.742] strutConnector(Clone)(Clone) added to ship - part count: 16
[LOG 04:01:14.743] stage count is: 2
[EXC 04:01:39.988] NullReferenceException: Object reference not set to an instance of an object
[WRN 04:01:47.496] [HighLogic]: =========================== Scene Change : From EDITOR to EDITOR =====================
[LOG 04:01:48.062] No Input Locks in effect right now
[LOG 04:01:48.453] ------------------- initializing editor mode... ------------------
[LOG 04:01:48.454] editor started
[LOG 04:01:49.069] Tocke 13 loaded!
[LOG 04:01:49.099] Tocke 13 - Tocke 13
[EXC 04:01:52.898] ArgumentException: GUILayout: Mismatched LayoutGroup.Repaint
[EXC 04:01:52.919] ArgumentException: GUILayout: Mismatched LayoutGroup.Repaint
[EXC 04:01:52.940] ArgumentException: GUILayout: Mismatched LayoutGroup.Repaint
[EXC 04:01:52.961] ArgumentException: GUILayout: Mismatched LayoutGroup.Repaint
[EXC 04:01:52.983] ArgumentException: GUILayout: Mismatched LayoutGroup.Repaint

Do you have the KSP_Folder/KSP_Data/output_log.txt of this? KSP.log is rather useless as it doesn't give enough info :)

I also had this issue with 1.5.6 while connected to a DMP Server (with 3 players).
Creating Subassemlies always ended in a freezed game. However, I couldn't reproduce the bug yesterday. Might be that I was the single player on the server, not really sure.

Connected to a remote server, single player online.

TestCase: Start assembling a space ship, take any parts and drop them on the subassembly. The subassembly window does not open, the parts are still visible (as if dropped). Using of existing assemblies works. It's not clear why sometimes creating them works, sometimes not.

The game does not freeze, repositioning the camera works, but the whole GUI is unresponsive.

output_log spams the following exception endlessly:

ArgumentException: GUILayout: Mismatched LayoutGroup.Repaint
at UnityEngine.GUILayoutUtility.BeginLayoutGroup (UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options, System.Type LayoutType) [0x00000] in :0

at UnityEngine.GUILayout.BeginVertical (UnityEngine.GUIContent content, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) [0x00000] in :0

at UnityEngine.GUILayout.BeginVertical (UnityEngine.GUILayoutOption[] options) [0x00000] in :0

at DarkMultiPlayer.PlayerStatusWindow.DrawContent (Int32 windowID) [0x00000] in :0

at UnityEngine.GUILayout+LayoutedWindow.DoWindow (Int32 windowID) [0x00000] in :0
at UnityEngine.GUI.CallWindowDelegate (UnityEngine.WindowFunction func, Int32 id, UnityEngine.GUISkin _skin, Int32 forceRect, Single width, Single height, UnityEngine.GUIStyle style) [0x00000] in :0

(Filename: Line: -1)

Fixed quite a while ago via 4d59953