Stencil not working unless H+V tiling is on, and paints with an offset

Guys, I'm surprised at myself that I am suddenly unable to use stencil. As a thousand times ago, I have a fill layer which I want to reveal only partially, so I add a black mask, a Paint layer under the mask, select a brush and a stencil, and try to paint on it with white color.

Nothing is painted unless I select H+V tiling (which I don't want, but it could be a trade-off). However, the painted area is not the one bordered by the stencil, but it's a little bit shifted to some directions. I've tried tri-planar and UV mode for the fill layer, as well as Tangent wrapping and planar (if I remember well the names of the paint layer's modes), with no change in the result.

I've recorded a short video. Can you spot what the basic thing am I miss or do wrong? (Substance Painter is up-to-date, and I fight with it on Windows 11.)

Thanks,

Gus