When I plug headphones into my 2011 17-inch MacBook Pro, the jack goes in and then I need to lightly force the last few millimeters. Then the sound goes out for a few seconds before it plays through the headphones. Is this normal? I never had to force the jack into my old MacBook Pro and the sound came onto the headphones instantly. I've tested Apple earbuds and AKG K44 headphones and the issue occurs with both. Thanks!