Dear @sstore23
Welcome to UQLab!
Could you please report the LOO error?
You can find a fruitful discussion in Acceptable LOO Error to learn more about this magic test.
Besides, try a bigger adaptive degree range by using:
MetaOpts.Degree = 1:30;
and q-norm-Adaptive PCE by:
MetaOpts.TruncOptions.qNorm = 0.5:0.1:1;
I hope this helps
Ali