Basically I'm trying to prompt you to learn how to read Ruby error and backtrace messages.
“filename:lineNo: inmethod”‘ or “filename:lineNo.”`

http://ruby-doc.org/core-2.2.4/doc/syntax/exceptions_rdoc.html
http://ruby-doc.org/core-2.2.4/Exception.html

@medeek said:

Okay 95% of that just went over my head, but I'll try and decipher into terms I can understand.

An example in Ruby of testing if an object reference is pointing at an object of a certain class:
if obj.is_a?(NilClass)
... or ...
if obj.is_a?(Float)

An example in Ruby of validating that an object reference call responds to a certain method call:
if obj.respond_to?(:methname)
... and testing for the "asterisk" method specifically:
if obj.respond_to?(:*)

@medeek said:

But why would this error only be raised for SketchUp running on MacOS and not Windows?

I don't know (offhand) as I avoid Macs myself. (But OSX and MS Windows use different sets of keycodes.)

Actually, looking at the backtraces (in your original error listing) the errors are kicked off by a LButtonDown keypress, but are occurring in the `` create_timber_geometry()`' method, lines 1064 and 1355.