UMG brush of border overlaps child tileview

Hello,
if I place a TileView inside a border element and set the border brush to draw as box/image the TileView disapears. If I use a texture which has invisible parts or set the brush to be not fully opaque the tileview shines throught.

Working if not placed inside border

Shining throught if border is not fully opaque

Using a texture (overlapping)

Hierachy tree (Units-Tab <— tileview but problem also exists if I place tile view directly)

282401-3.png

Is it a bug? Am I doing something wrong?