Power loss after song exported

Hi and thank you very much in advance for any help or advise.

I have recently exported a song and at the same point (the chorus) during the mix each time it sounds as if the power has been sucked out of the music, there is a noticeable dip in volume, almost as if that part of the song is in some sort of vacuum. This doesn’t occur when you listen back to the track on the screen though. Ive no idea what could be causing the problem? Is there anything I should be checking at all? Thank you again.

P.S as you can tell I’m very much a beginner!