I believe there are changes to AppLauncher in 1209 that confound KER in the VAB/SPH.
From KSP.log:
KerbalEngineer.Editor.BuildAppLauncher.Update () [EXC 19:18:22.185] MethodAccessException: MethodKSP.UI.UIRadioButton:get_Button ()' is inaccessible from method KerbalEngineer.AppLauncherButton:Disable ()'
I believe there are changes to AppLauncher in 1209 that confound KER in the VAB/SPH.
From KSP.log:
KerbalEngineer.Editor.BuildAppLauncher.Update () [EXC 19:18:22.185] MethodAccessException: Method
KSP.UI.UIRadioButton:get_Button ()' is inaccessible from methodKerbalEngineer.AppLauncherButton:Disable ()'
Ad infinitum...
Log files