Blender Version
Broken: all since 2.7x
Worked: never

Short description of error
Only Insert Needed option in animation preferences, overrides manual keying hence making manual keying unusable.

Exact steps for others to reproduce the error

Select your default cube,
create a keyframe in frame 1
create a keyframe in frame 10
go to preferences > animation
activate the Only Insert Needed option.
go to frame 5, try inserting a keyframe with, I (menu) or in the animation editors.
message comes up: "Keying set failed to insert any keyframes"

this makes the option needed to be turned off everytime that you want to force a keyframe which is broken.

any further info let me know.