Sounds like maybe a timing or counting issue. When playing with others it's even more important that you keep proper count with the time signature otherwise you'll miss your mark. Perhaps the other person is better at that than you or has heard the song many more times so they're more familiar with the changes. It's nothing to beat yourself up over. Everyone learns at different pace. Try playing the song on your own for a while at the proper time signature before playing with your friends. See if that helps.

Good Luck,

Moe