A solution to fix the instability was created base on remark 30062#c78604 from 2018-08-14 16:10.
//the situation when degenerated edge already exists but flag is not set
//(i.e. the parametric space is closed)
GeomAdaptor_Surface& Ads = mySurf->Adaptor3d()->ChangeSurface();
- Standard_Real max = Max ( Ads.UResolution(myPrecision),
- Ads.VResolution(myPrecision) );
+ Standard_Real max = Max ( Ads.UResolution(precVtx),
+ Ads.VResolution(precVtx) );
if ( p2d1.Distance (p2d2) /*Abs (par1 - par2)*/ <= max + gp::Resolution() ) return Standard_False;
//#84 rln p2d1 = aP2d.XY() + par1 * theDir2d.XY();