thermal expansion simulation

Hi, I have an interesting problem to solve. I have coaxial resonator and I want find out its resonant freauency depending on temperaure. The influence of temperature ais modelled as alllenghts enlarementd depnding on one variable. The problem is that CST produces some jumps in the graph. Could anyone advise how to get rid of? I mean has anyone experience with eg. mesh or simulation precision in CST for modal analysis calculation or some point to any information sources?

Thanks