Principal Stress check in RM Bridge

Dear Mrs./Mr.

In my calculation, I'm using RM-Set to plot SIGI principal stress of concrete box girder. As the results plotted, I observed that there is some elements (el. 124, 127, 157 & 160) has a confusing principal stress result, SIGI princ. stress of thóe elements are very large in compare to adjacent elements, although these elements have similar section properties and internal forces.

After checking PrincLC results, section properties etc. I can not spot any irregular data, so I don't have any idea why principal stress results are so confused, can you please check my model and give me some advices, thank you.