MPNowPlayingInfoCenter not reacting properly when pausing playback

I’ve the solution! Set only the MPMediaItemPropertyPlaybackDuration

1 – When you start the track, set the property with the total duration of the track:

MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
NSDictionary *songInfo = @{
    MPMediaItemPropertyTitle: title,
    MPMediaItemPropertyArtist: artist
    MPMediaItemPropertyPlaybackDuration : [NSNumber numberWithFloat:length]
};
center.nowPlayingInfo = songInfo;

2 – when you pause the track… do nothing.

3 – when you play the track, set the property with the currentTrackTime:

MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
NSMutableDictionary *playingInfo = [NSMutableDictionary dictionaryWithDictionary:center.nowPlayingInfo];        
[playingInfo setObject:[NSNumber numberWithFloat:player.currentTrackTime] forKey:MPNowPlayingInfoPropertyElapsedPlaybackTime];            
center.nowPlayingInfo = playingInfo;