Offset curves causing problems with curve parameters

Hello all

If I have a polyline and I offset it 'outwards,' the curve parameters (t) do not behave as one might expect. For the original curve - the one that was not offset - the curve parameters are consistent with the length of the curve (ie for a 3m curve evaluated at halfway (t) would be 1.5). This is also true for the one that was offset 'inwards.'

For the one that is offset outwards the (t) value is consistent with the curve length up to the first discontinuity (ie the first kink). After that the parameters do not relate to the length and only increase slightly from (t) value at the first kink.

I've attached a picture of this, and tested it in version 0.9.0014 in Rhino 5 and 4... The same applies with lines imported from Autocad and Microstation, as well as those drawn in Rhino. A solution to this would be much appreciated, as I swear it used to work - I have a script that draws seats for a stadium that worked on this principle and been using it for a while without any problems, although not for a few months, possibly before the install of grasshopper 0.9.0014.

Thanks