Rigid Body Modes Error


I am new to Grasshopper and have been trying it out in conjunction with Karamba. I have started simple with lines converted to beams, for further analysis with Karamba, however, no matter what I do I keep getting the same error (see below).

I have simplified my model down to one line connected to another line, to try and get the model working, however the same error occurs. I believe it it something to do with the connection between the two beams, but I have tried everything I can think of to fix it, but nothing is working.

Below is an image of my model, and I would really appreciate any help in fixing this error message I keep getting!

Thanks in advance,