Brett probably had to deal with something and that was one of the reasons why he couldn't go to Hayden earlier. It's kinda obvious that he was not loving their break up either already 2 years ago (i refer to flashback episodes here and Bretts reaction when Scott mentions him). Who/what was Brett dealing with could have something to do with the new witness, but no one knows yet who it is

I just love their dynamic right now. Hayden is doing everything in his power to push Brett away, even though he already showed his hand the moment they saw each other again… like, come on broo...
And Brett, the mastermind who’s usually two steps ahead of everyone, is 100 percent sure he’s getting Hayden back. I mean, even a blind person could tell that Hayden still has feelings for him. Yet when it comes to himself, bro is like a 1000 steps behind. He still hasn’t realized that he’s in love with Hayden.
And here I am, suffering through the flashbacks (I know they’re important, but still) and waiting for the rut episodes, because those are going to blow my mind.