First, let me say I hate that the tangent line of HSS & Angles can not be treated separately from the Visible Lines. That being said, I'd need to see the Presentation rule for that Model Object in the "Objects Presentation". It could be that the geometric constraint for non-linear beams is set to "(Visible(Exact)Hidden)"
If you find the "Presentation" set to exact, change it to "VisibleHidden"