Make entities stay attached when constrained

I wonder if anyone can shed any light on an issue I am having with constraints.

I am having a lot of difficulty making entities which I have constrained, staying connected to each other.

They aren't connected end to end, but must stay in contact with each other.

In the attached drawing the arcs in the corners need to be always in contact with two lines which are vertical and horizontal.

The straight line connected to one end of the arc will move closer or further away from the corner dependant on the parameter "M"

The angled line at the other end of the arc must stay at a set angle and always be a set distance (virtual distance as it doesn't touch it) along the straight green line.

Neither of the two lines connected to the arcs are touching the corner where the two green lines meet, so the arcs need to adjust in radius whenever other parameters are altered
so they are always tangent to the connected lines mentioned earlier and must always be touching the corner where the green lines meet and be on the outside.

I have attached my parameterized drawing which is failing and to the right of it is how the arcs should be connected.

I set constraints for the arc to be connected to the two green lines (coincident constraint using entity and point options).

I can't understand why I can change some of the dimensional constraints and instead of the arcs staying in contact with the green lines, they just moves inwards and is no longer touching its constrained point.

The least I would have expected if the geometry change wasn't possible would be for the drawing to remain as it was, but it breaks its own rules by disconnecting itself from the constrained point.

I know that what I am asking is geometrically possible as I do it all day everyday, I just can't figure out what I need to tell the drawing for it to behave as I require.

If anybody would like to have a look and see if they could help that would be much appreciated.

If what I am experiencing is a bug I will submit a support request.

Many thanks in advance.