Typically the rhythm guitarist, drummer and bass player set the groove. If they're not locking, then the drummer and bass player should set the groove, especially for R&B. The drummer, bassist and guitarist should all play on the same place within those cute little Gaussian curves that are the beat.
What I hear in your question is that the rhythm section isn't locking and you want to know why.
So the first thing to do is play to a metronome or drum machine. Are you all playing at steady tempo throughout the song with and without the metronome? Or does the metronome appear to speed up and slow down to one or more of you?
If tempo's okay, then start the drummer playing with the metronome as far behind the beat as you want. Then have the bassist come in and hit the same beat. Then you come in.
Do this for a few minutes and hopefully everybody will be on the same page. Try playing the song again.