I'm using a brand new 2018 MacBook Pro 15 inch (16GB RAM, 200GB free space currently on SSD). SourceTree is extremely slow when doing server checks it seems.
I previously used SourceTree with the same repo on my 2012 MacBook Pro and it was significantly faster.
Every time I click on a commit in the browser that is origin or switch back from that to a another one, the ball keeps spinning for 5-7 seconds. My internet speed is quite fast and it works fine on my other machine.
I switched to using the system git because previously it was completely unusable. It's a bit better now but still have the 5-7 seconds lag and performance problems when committing, etc.
I tried downgrading to 2.5.3 as recommended in some similar posts but that did not work either.