This is probably a duplicate of Mouse acceleration while painting - Programming & Scripting - Unreal Engine Forums, but since that one was not posted as a bug report, I figured it would be best to report it again, here.
On the latest macOS 10.12, it is impossible to use the paint or sculpting tools properly. Moving the mouse works just fine, but as soon as a mouse button is clicked (and thus, painting is started), the mouse becomes… unpredictable. It feels like the sensitivity randomly jumps up and down.
It is incredibly hard to describe verbally, so I recorded a screen cast and attached it (mp4 in zip). Here, I’m first moving my mouse in a circular pattern, without clicking. Then, I click and hold the left mouse button, while doing exact the same hardware inputs. It is clear that mouse movement not only gets slowed down (which could be okay), but also, the radius increases and I am no longer drawing a circle, but a … random egg shape. At second 38, you can see the mouse drift off in the distance, and there is no way to counter that drift.
Sometimes, the mouse randomly jumps off-screen. Sometimes, while drawing, the editor crashes. I submitted crash reports for them, but just for reference, here is a stack.
I am aware that this sounds like I am drunk while drawing (I’m not!), but believe me, this is an issue, that, sadly, renders the editor almost useless on macOS.
Edit: My stack looks very similar to the one in UE-49008, and apparently, a fix is already landed for 4.18? Is there any way for me to test that, and maybe confirm that this issue is resolved?