Shackle will not render with "normal" bevel

[crabbedh]

I'm using a normal shackle routine that I've gleaned from PPP examples of lock puzzles using shackles. The shackle in question won't render if the bevel is beyond about 0.8. If you render part of the shackle in two separate parts (the arc is broken up) then bevels work fine.. I've tested up to about 1.5. I'm not sure if this is a problem with PuzzleCad or OpenSCAD or may be a math precision problem. Not wanting to invest the time into learning the depths of OpenSCAD, I thought someone more knowledgeable might take a look to see the issue. I've included the code and tried to strip out anything unnecessary. The arc() routine is not mine, but taken from a PPP example. I've included the SCAD source and a couple of screen shots. I'm using the 2.3.1 release on macOS. The top screen shot shows the error of 'no render' with bevel of 1.. The bottom is if I change the bevel value to 0.7.


shackleProblem.scad.zip