facing difficulty while interpreting mean-variance trend plot in GEO2R

Question

[ElfoHelpo]

Hi, I am beginner in analyzing GEO array database.

I got this Mean-variance trend plot result while I assess one of GEO series array data (GSE15790), with 'Apply adjustment to the P-values - none' and 'Force normalization- yes'. (other options are as default) I got surprised to have this awkward plot with divided at middle, and x-axis ranging from 8 to 16. And the expression density plot shows something weird. Are these plots meaning some mistake in the normalizing process? or error in array data? As there aren't many processes in GEO2R, I don't think I did something wrong. please someone give me some opinion.

Thanks in advance,