MechJeb Version

dev 910

KSP Version

1.8.1

Description

Even solid retro booster engines with
allowShutdown = True
are not shut down.
It says

... and can be shutdown using "SolidSafe" technology ...

but that does not work.
And the MJ setting "Module disabling does not kill throttle (RSS/RO)" was not turned on.

Replication Case

Use the Coatl Aerospace "Landvermesser" and use the "CA-SB15 Landvermesser Solid Rocket Retromotor" to deorbit or even change inclination with the MJ Landing Guidance.
The engine does not turn off when the thrust lever goes to 0.

KSP.log

Full log:
https://www.dropbox.com/s/m6000vou81aot3m/player.log%20and%20stuff%202019-11-24-01.zip?dl=1

Could be related:

MechJeb module MechJebModuleStagingController threw an exception in OnUpdate: System.NullReferenceException: Object reference not set to an instance of an object
  at MuMech.MechJebModuleStagingController.HasDeactivatedEngineOrTankDescendant (Part p) [0x00000] in <3ddb09b54c5e42379c1671957c9d0f6f>:0 
  at MuMech.MechJebModuleStagingController.InverseStageDecouplesDeactivatedEngineOrTank (System.Int32 inverseStage, Vessel v) [0x00024] in <3ddb09b54c5e42379c1671957c9d0f6f>:0 
  at MuMech.MechJebModuleStagingController.OnUpdate () [0x00144] in <3ddb09b54c5e42379c1671957c9d0f6f>:0 
  at MuMech.MechJebCore.Update () [0x00192] in <3ddb09b54c5e42379c1671957c9d0f6f>:0 
 
(Filename: C:\buildslave\unity\build\Runtime/Export/Debug/Debug.bindings.h Line: 35)

Cross reference to older issue of the exact same part:
raveloda/Coatl-Aerospace#66

also check
raveloda/Coatl-Aerospace#81

And another one:
raveloda/Coatl-Aerospace#83

I start to believe that Coatl is WIP for real ...

So, now after pushing some commits to Coatl at least the SRM is stageable. And can be shutdown by right-lick (bruh) or action group.