I finally found a texture solution (95% ok) to depicting gear teeth visually, but not in tooth detail. Which is all I need for this model. It is not perfect, especially for bevel gears, but can be made to look reasonable.
This does not mean I don't want to know why the crashes happened, but I'm posting a trial ring with the texture applied, in case anyone needs to depict gears.
This way I can show gears with a bare minimum of lines drawn, and maintain solidity.
As an added bonus, I can make them straight gears or (in this case) helical bevel gears by simply rotating the texture in situ. TIG's "TextureRotate.rb" ๐ ๐
Select the material "Gear Teeth" and edit it. By adjusting the aspect ratio you can adjust the gear tooth pitch. Best to break the aspect ratio link to do that.
Visual (Non 3D) depiction of gears by texture.