Comment 3 for bug 1029584

The colored paths in 'line_stroke_bugs.svg' are using a custom dash array which is not among the stock dasharrays as defined in the default preferences file (which are based on a 1px stroke width):

0.375 px stroke and dasharray:3,1
corresponds to
1.0 px stroke width and dasharray:8, 2.66666667

Dash arrays are using absolute units (Inkscape only supports default px user units currently). To keep them proportional relative to the stroke width, Inkscape recalculates them whenever the stroke width changes (can be easily verified via XML Editor: draw a new path (defaults to 1px width), apply stock dash style, and watch the dasharray update whenever the stroke width is changed).

Note: custom dasharrays are currently not supported in the GUI:
 Bug #170233 “A window for editing dash arrays”
 Bug #172164 “Custom dash patterns”
 Bug #512242 “Custom dashed lines impossible without the XML editor”

Workaround for this specific file: quit Inkscape, open the preferences file, add you custom dasharray to the group 'id="dashes"':

      <dash
         id="dash-8-2.66666667"
         style="stroke-dasharray:8,2.66666667" />