Why I am getting negative Total Energy when using preload springs (Hypermesh, Radioss)

Hello,

I am building a model in which I have plenty of preload springs that are deactivated at t=0. When a sensor is activated (generally distance between nodes becomes lower than a certain value) those springs start working.

The general behaviour in the animations seems to be logical. However, when I check the TH outputs, I see the Total Energy has decreased a lot, getting to greatly negative values. These values correspond to Internal Energy, in particular Spring Internal Energy corresponding to the springs that have been activated during the simulation. 

In 0001.out file after simulation the %Error in energy is 0.00%, and the mass added is less than 5%.

I cannot make physical sense of this result, as I tend to think that the energy disipated in those springs should have been transferred to the attached elements via kinetic energy in rigid bodies, or deformation (ie internal energy) in shell elements. This is why I am concerned the dynamics I am seeing at the animations are not realistic, as those springs may not be working as intended.

Can anybody give a pyhisical explanation on this? Is my model still valid or am I missing the effects of the springs in the global model in any way? If so, how can I model my springs so that I remove this undesired effects?

Thank you in advance

Diego