Specific vertices shoot off in random directions when bevelling I am currently trying to create a basic wheel-like shape to test out blender and work out some of the key shortcuts on Mac.

I am encountering an issue when I try to bevel specific edge loops, please see the pictures:

 

I fully anticipate that I have some sort of geometrical inconsistency - I have tried some options from mesh&gt;cleanup on the whole mesh object as detailed in this answer like 'merge by distance' or 'split non-planar faces' (I don't really actually know what that does but I hoped it might make any doubles more obvious). 

The issues pictured only occur on these edges, others around it are fine
This turned out to be an easy fix, somewhere along this line my 'surface normals' got all messed up, and Blender's vertices follow their respective surface normals when transforming like in the bevel tool.

To resolve this problem (unless you have custom surface normals and resetting isn't an option) is to simply select the area which is not behaving as expected (in this case the edge loops and recalculate normals. For Mac the shortcut for this is shift + N. 

See more about it here