jit.gl.sketch/gllinestipple - flakey behavior?

Letraset Catalogue's icon

I'm trying to render diagram style dashed lines using jit.gl.sketch with gllinestipple. The results are pretty flakey thus far. Dashes appear to flicker and even roll?

See attached - any help would be greatly appreciated.

I'm using:
MacBookPro1,2
Intel Core Duo
2.16 GHz
ATY,RadeonX1600

2690.dashedlines.maxpat
Max Patch