Don't believe that it will help you, but nevertheless I will write how it was with the GU for us. An expert wrote that the windows will not be accepted because they are too heavily soiled. The GU commissioned a company for the cleaning. Afterwards, the expert walked from window to window with the GU and my husband and recorded scratches. Scratches in the visible area - replacement, smaller dents were a few euros (negligible), dents invisible without functional impairment bad luck (okay, I can live with that). The windows were taped inside and outside from the beginning, nevertheless, for example, screed got on them. Our construction site was quite tidy and relatively clean. The front door was wrapped very thickly. No damage from construction, but removing everything and the adhesive residues was a huge task. Windows were replaced without objection, even a window where the expert himself said scratches were indeed in the visible area but hardly visible. When you consider how smoothly the whole thing went and the GU cannot say to the client that it wasn’t them, the windows may initially cost more. Was it more expensive overall? If yes, my nerves were worth it to me. Isn’t it the task of the architect/construction management to ensure that no damage occurs and if so, to regulate who is responsible or how high the retention is? Fingers crossed for you. I would charge everyone you can nail down with photos. Rejection, I think, is normal at first.