Selection keeps popping out in layer mask and I can't delete it

[blogsofwardotme]

As you see from layers, I copied pasted an area from the bottom layer to a top layer to cover the tube.Than I added a mask next to the "patch" to
remove the excess of the patch. As I click on the bottom layer, the green line goes away just by clicking. As I go back to the mask and click on it,
the green lines reappear and shift command a doesn't work. The selection prevents me from painting in the mask.
Strange thing as you see I already started painting but I can't replicate it. Thanks

[Ofnuts]

Screenshot image is way too small to be usable (better give a full size JPEG than a scaled down small PNG).

If Select > None is disabled there is no active selection, and if it isn't, just used it top remove any unwanted selection.

Remember that you cannot paint the layer (or its mask) outside the layer boundary (but what would be the point of painting the mask outside of the layer)

Looking at the controls it appears to be Gimp v3. The green line is the layer boundary (It is green when the mask is selected, instead of yellow when it is the layer). Clicking on the bottom layer should make it appear (in yellow) around the whole image (boundary of the bottom layer). This is not the selection indicator, which is moving (marching ants).