Fill the corner at the window - Styrodur etc.

Hello colleagues, Our house will be plastered next week and by then 3 corners of the house need to be filled. The window frame is made of aluminum, the roller shutter boxes are made of plastic, and insulation made of Styrofoam is applied above. Gluing Styrodur would probably work, but it cannot be glued to aluminum because there is too much play. The only possible solution would be to attach a chipboard and then glue or screw the desired corner onto it. The question is, does anyone here have experience with how the corners may be filled? Is there maybe a technical drawing for how it may be done? I would appreciate your suggestions. Photos of the window are attached. In one photo, the corners have already been filled with Styrodur, but had to be removed again due to the aluminum play. The second photo shows the corner that needs to be filled. Many thanks in advance for your experiences with this window problem

these are thermally critical corners. The respective trade (window manufacturer, energy consultant, construction supervisor) should have thought about this IN ADVANCE - right? I know it like this: outside (from window corner to window corner), color-matched profiles made of the same material (aluminum / plastic) are installed, which then form a visually pleasing transition. Mostly glued or riveted. Sometimes screwed as well. Presumably, these cavities that then arise are insulated (foamed?).

Ahem... What does the window builder/metalworker say? That is primarily his original task. And what does the architect say? Can't that be insulated with stone wool or something similar? Then rivet/screw on a large angle bracket? The aforementioned responsible parties should be able to specify and carry that out for you.

What does the one who planned this corner say?

The architect says that it would be better to bridge the aluminum spacer with an OSB board first and then glue the Styrofoam board on top, so that there is no play between the materials. Since the conditions do not allow for mounting the OSB board in any way, gluing remains the only option, but with a gap to the aluminum. Does anyone know if the OSB board could also be screwed to the shutter boxes in an emergency?

So, I have now spoken with the window manufacturer. Screwing in 1 cm from the outside or inside is allowed here.