To avoid such situation always use an interposing relay between the radio's remote power wire and the power radio antenna. Normally audio players have got 350mA(max) provision to operate any thing external which is enough to operate a smoothly operating antenna, but with the passage of time the antenna mast gets dirty or sometime even bends (kids have a tendency to pull the mast when extended) in that case the internal motor has to apply more force and as a result draws more current than normal.
In my car I have used antenna (half) switch and the antenna remote power is taken from the accessory power (ignition switch). If the acc power is turned off the antenna retracts fully no matter the switch is on or off. But the antenna extends when both the acc power is present and the switch is made.