Issue with modelling steel beam-column interaction

I am using Ruaumoko 3d to perform NLTH analysis on some steel moment resisting frames I have designed.

While verifying the hysteresis rules that I have used in my analysis I came across a problem which I was hoping someone might be able to help me with. For the columns of MRFs I decided to use an elasto-plastic hysteresis rule and to include the steel beam-column interaction incorporated in the programme (IBEAM=3). The interaction equations seem to work however the problem I am having is that when IBEAM is set to equal 3 the hysteretic behaviour stops being elasto-plastic and becomes bilinear. The output file lists the member properties as being elasto-plastic but lists a post-yield stiffness of 0.01 (or 1%). In other words the response changes to bilinear with 1% post yield stiffness. If I change my input file to use the bilinear hysteretic rule with r=0 the output still uses r=0.01. In fact with IBEAM set to 3 the r value becomes 0.01 regardless of what value I input. I have no problems if I remove the beam-column interaction.

Therefore I was wondering if anyone knew whether there was a reason that Ruaumoko does this or if it is possibly an error in the program.

Thanks for your help.

Owen