[Radio Wrangler]

Reinserted AM carrier in transmitters has to balance the phase of the carrier with the phases of the sideband components. Sometimes this is impossible because the sideband components have gone through a very tight filter. The sideband-carrier phasing has to be right at the receiver's AM detector because the carrier acts as the control for what amounts to synchronous detection. If the carrier is at 90 degrees to where it should be, your AM detector becomes more of an FM detector.

David