Renovation of the kitchen

Good day everyone, I have a small problem with the "wall" counter. I got myself a 3.75m long multiplex board (0.40m wide) + 4 steel brackets that should normally be sufficient. Yesterday I leaned on it and promptly the brackets tore out of the wall, I used sx6x4.5 Fischer plugs (3 per bracket). I drilled into the stone but maybe not far enough?!? Unfortunately, larger screws don't fit in the brackets, should I now use longer screws and plugs or does anyone have an idea which plugs would hold in the softer plaster? Many thanks in advance. Best regards Marcel

Hello !! I would suggest to you firstly other dowels (8) and secondly other, longer screws… Now there would be a few possibilities. The first would be to drill the holes of the brackets bigger so larger screws can go through, or secondly to return the brackets and exchange them for other brackets. An important question for you would be what kind of masonry do you have.. Best regards ; )

What are the measurements of the angles?