The 36-year-old comedian filed for divorce on December 30 after 14 months of marriage to Perry.
It has since been alleged that Brand became frustrated when the singer opened up to McCoy about their relationship troubles.
"They'd often speak at strange times of the night because they travel a lot," a source told Heat. "It's fair to say that she opened up to him about how hard her marriage had come. Travie never really 'got' Russell or their marriage."
The magazine claims that Perry's close bond with Josh Kloss, the model who appeared in her 'Teenage Dream' video, was also a cause of concern for Brand.
Recent reports have attributed their split to Brand's failure to control himself around Perry's deeply religious parents.
Brand admitted earlier this week that he began to crave his promiscuous past while married.
> Katy Perry speaks on Russell Brand divorce: 'My heart is happy again'
Watch Katy Perry in the video for 'The One That Got Away' below: