If the sender has not formulated the idea, thought or message in proper manner, it can result into a barrier in communication. The barrier occurs at what level?

If the sender has not properly formed the idea or message, the barrier arises at the level of the encoder.

Encoding is the sender's act of turning thought into symbols, so a poorly framed idea fails right there.

The transmission stage concerns the physical carrying of the signal through the channel, after encoding is done.

A fault at the end of the decoder would lie with the receiver's interpretation, not the sender's formulation.

A technical stage barrier involves mechanical or electrical faults in the medium, not the shaping of the idea.

The flaw here is at the point where the message is first framed for sending.