There’s not much you can do to avoid this problem with bold transformations. It does take some work to fix these intersecting co-ordinates, but once you have done a few it gets easier.
See the tutorial on Working with Transformations
You can also use the method in this tutorial thread for Reducing Nodes to Smooth Glyphs to remove the intersecting co-ordinates — it retraces the displayed contours to create new ones, which have no errors. Calculate the scale transform that you need to apply after pasting.
Since you have Scanahand, you can try another method that might be quicker.
- Ignore the intersecting co-ordinate errors, and just install the font as a temporary font
- Use the bold version to fill in the Scanahand template in IrfanView or a whatever.
- Run the template through Scanahand to create the bold font style, which should now have no errors