Sobol' total variance of multiple outputs are all 0 except the last one

UQ with UQLab Community Q&A and How To
1

There are multiple outputs (18) in my model. After I run sensitivity analysis with Sobol’ indices in UQLab 2.1.0, the total variance of the analysis results (1*18) are all 0 except the last one (more than 8.3).

  1. Is this expected?
  2. Actually I’m trying to calculate aggregated Sobol’ indices through the total variance, is it already included in the results?
2

I got similar results after running example “uq_Example_Sensitivity_04_MultipleOutputs.m”, listed as below:
0 0 0 0 0 0 0 0 7.87898251578865e-06
When we calculate sensitivity indices for each output, we need to know its total variance. so this result looks incorrect to me.