When I apply Posterize time effect on masked layers the masking fails.

I took an image showing multiple characters in that image, duplicated the image applied making on the top layer selecting the person of interest. Applied Black & White effect on the lower layer. Next, I took an adjustments layer and applied an effect called Posterize time effect and as soon as I applied it the masking behaves unpredictive.

With Posterize time activated.

Troubleshoot: 1. I tried to put this posterize effect on nested sequence of the two layers.
2. Without Nested sequence adding and adjustment layer on the top.​​​​​​​​​​​​​

Nothing works.