H'mmm, I have 'interesting' bug / problem that I think 'might' be associated with MJ...
I am running the latest release. I have a sat deployment system that has worked in previous releases. Now when I deploy one of the sats, I start getting exceptions thrown into the ksp.log. Even when i undock from the carrier, the same happens.

I have looked through the log(s) and here is the culprit, I think.

[LOG 17:42:05.645] RemoteTech: SatelliteManager: Register(ModuleSPU(, ca4df6d3-3cd0-4038-916e-ce5a2efe1500))
[ERR 17:42:05.673] MechJeb caught exception in core OnSave: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.MechJebCore.OnSave (.ConfigNode sfsNode) [0x00000] in :0
[ERR 17:42:05.832] MechJeb module MechJebModuleThrustController threw an exception in Drive: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.CelestialBodyExtensions.RealMaxAtmosphereAl titude (.CelestialBody body) [0x00000] in :0
at MuMech.VesselState.TerminalVelocity () [0x00000] in :0
at MuMech.MechJebModuleThrustController.TerminalVeloc ityThrottle () [0x00000] in :0
at MuMech.MechJebModuleThrustController.Drive (.FlightCtrlState s) [0x00000] in :0
at MuMech.MechJebCore.Drive (.FlightCtrlState s) [0x00000] in :0
[EXC 17:42:05.838] NullReferenceException: Object reference not set to an instance of an object
[EXC 17:42:05.856] NullReferenceException: Object reference not set to an instance of an object
[LOG 17:42:07.311] Target: None

[EXC 17:42:07.334] NullReferenceException: Object reference not set to an instance of an object
[EXC 17:42:07.349] NullReferenceException: Object reference not set to an instance of an object
[EXC 17:42:07.400] NullReferenceException: Object reference not set to an instance of an object
[EXC 17:42:07.415] NullReferenceException: Object reference not set to an instance of an object
[EXC 17:42:07.458] NullReferenceException: Object reference not set to an instance of an object

Please let me know of any other info, tests or such that I can provide.
Thanks sarbian for all of your fantastic work. MJ is the #1 mod for me......

Just tried again, this is when the capsule jetisoned the farings and was ready to turn around and come back for the satellite deployment pod...

[LOG 22:50:35.850] [KzProcFairingSide1]: Activated
[ERR 22:50:35.911] MechJeb caught exception in core OnSave: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.MechJebCore.OnSave (.ConfigNode sfsNode) [0x00000] in :0
[EXC 22:50:36.064] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.083] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.099] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.112] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.161] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.174] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.190] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.204] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:50:36.217] NullReferenceException: Object reference not set to an instance of an object

oops did not want to close, wrong button

And here is the log for when i completed the docking.

[EXC 22:55:03.774] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:55:03.788] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:55:03.801] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:55:03.813] NullReferenceException: Object reference not set to an instance of an object
[EXC 22:55:03.825] NullReferenceException: Object reference not set to an instance of an object
[LOG 22:55:03.848] Docking to vessel Kerpollo-IIx FBigBoosterII_KerKomDeployTESTER
[LOG 22:55:03.981] Camera Mode: AUTO
[LOG 22:55:03.987] stage manager resuming...
[LOG 22:55:03.992] [Orbit Targeter]: Target is null
[LOG 22:55:56.714] Game Paused!
[LOG 22:55:58.858] Flight State Captured

I dropped down to load #146 and repeated test. here is the error from ksp.log
This one just threw the two errors and did not keep dumping the NullReferenceException's on and on and on.....

[WRN 23:01:24.571] Only custom filters can be played. Please add a custom filter or an audioclip to the audiosource (RLA.rcs45).
[ERR 23:02:01.166] MechJeb caught exception in core OnSave: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.MechJebCore.OnSave (.ConfigNode sfsNode) [0x00000] in :0
[ERR 23:02:01.312] MechJeb module MechJebModuleThrustController threw an exception in Drive: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.CelestialBodyExtensions.RealMaxAtmosphereAltitude (.CelestialBody body) [0x00000] in :0
at MuMech.VesselState.TerminalVelocity () [0x00000] in :0
at MuMech.MechJebModuleThrustController.TerminalVelocityThrottle () [0x00000] in :0
at MuMech.MechJebModuleThrustController.Drive (.FlightCtrlState s) [0x00000] in :0
at MuMech.MechJebCore.Drive (.FlightCtrlState s) [0x00000] in :0
[LOG 23:02:33.980] RCS lock/unlock
[LOG 23:03:54.332] [Orbit Targeter]: Target is KzInterstageAdapter
[LOG 23:06:26.933] Docking to vessel Kerpollo-IIx FBigBoosterII_KerKomDeployTESTER

load #145 produces the following. Note: after the initial undocking and the error hits, the music in ksp starts 'stuttering' (starts and then restarts, every few seconds. like memory overwrite or such)

[LOG 23:14:51.834] RCS lock/unlock
[LOG 23:14:54.462] RCS lock/unlock
[ERR 23:15:19.602] MechJeb caught exception in core OnSave: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.MechJebCore.OnSave (.ConfigNode sfsNode) [0x00000] in :0
[ERR 23:15:19.752] MechJeb module MechJebModuleThrustController threw an exception in Drive: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.CelestialBodyExtensions.RealMaxAtmosphereAltitude (.CelestialBody body) [0x00000] in :0
at MuMech.VesselState.TerminalVelocity () [0x00000] in :0
at MuMech.MechJebModuleThrustController.TerminalVelocityThrottle () [0x00000] in :0
at MuMech.MechJebModuleThrustController.Drive (.FlightCtrlState s) [0x00000] in :0
at MuMech.MechJebCore.Drive (.FlightCtrlState s) [0x00000] in :0
[LOG 23:15:34.868] RCS lock/unlock
[LOG 23:15:46.060] [FLIGHT GLOBALS]: Switching To Vessel Kerpollo-IIx FBigBoosterII_KerKomDeployTESTER Probe ----------------------
[LOG 23:15:46.402] stage manager resuming...

#144 has the repeating Null when undocked and then fixes after re-docking. Same stutter in sound is present as well...

undocking

[WRN 23:25:40.313] Only custom filters can be played. Please add a custom filter or an audioclip to the audiosource (RLA.rcs45).
[ERR 23:25:58.136] MechJeb caught exception in core OnSave: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.MechJebCore.OnSave (.ConfigNode sfsNode) [0x00000] in :0
[ERR 23:25:58.387] MechJeb module MechJebModuleThrustController threw an exception in Drive: System.NullReferenceException: Object reference not set to an instance of an object
at MuMech.CelestialBodyExtensions.RealMaxAtmosphereAltitude (.CelestialBody body) [0x00000] in :0
at MuMech.VesselState.TerminalVelocity () [0x00000] in :0
at MuMech.MechJebModuleThrustController.TerminalVelocityThrottle () [0x00000] in :0
at MuMech.MechJebModuleThrustController.Drive (.FlightCtrlState s) [0x00000] in :0
at MuMech.MechJebCore.Drive (.FlightCtrlState s) [0x00000] in :0
[EXC 23:25:58.392] NullReferenceException: Object reference not set to an instance of an object
[EXC 23:25:58.410] NullReferenceException: Object reference not set to an instance of an object
[EXC 23:25:58.425] NullReferenceException: Object reference not set to an instance of an object
[EXC 23:25:58.437] NullReferenceException: Object reference not set to an instance of an object
[EXC 23:25:58.449] NullReferenceException: Object reference not set to an instance of an object

then re-docked.

[EXC 23:27:18.203] NullReferenceException: Object reference not set to an instance of an object
[EXC 23:27:18.216] NullReferenceException: Object reference not set to an instance of an object
[EXC 23:27:18.230] NullReferenceException: Object reference not set to an instance of an object
[EXC 23:27:18.243] NullReferenceException: Object reference not set to an instance of an object
[LOG 23:27:18.264] Docking to vessel Kerpollo-IIx FBigBoosterII_KerKomDeployTESTER
[LOG 23:27:18.531] Camera Mode: AUTO
[LOG 23:27:18.537] stage manager resuming...

Closing this as an old MechJeb issue. Many MechJeb issues have had little interest in years, have been fixed for years, do not include adequate replication steps, refer to old problems which are no longer applicable, or are difficult to determine what the problem is. This issue is being closed for one of those reasons. We apologize for any inconvenience, but keeping the TODO list tidy helps the developers.

If this bug/issue is still a problem, please open a new issue. For bugs please try to include a Minimal, Complete, Verifiable Example that explains all the steps required to replicate the issue. A link to the KSP.log file should be ideally included, but is often not sufficient information. Screenshots or short videos are often the best way to show a bug.