We have a team that uses SourceTree on Windows and Mac machines, with 2-3 people working on the same repository at the time.
There's a common problem among all Mac users that Sourcetree is slow or problematic. When a Pull or Push is being done, SourceTree hangs up and it takes a long time for the task to complete.
Here are the system specs and versions :
OS: 10.12.6 Mac OS Sierra
SourceTree: 2.6.3
Git: 2.10.1
GitLFS: 2.0.2
Bitbucket Media Adapter: 1.0.6
This happens much less regularly on a Windows machine ; there, we resolve the problem by running git pull on the command line.