Hello Sketchfab Team!
The case happened with the model below, where the center button of the washing machine (with PBR materials) had a glossiness of 86 (leaving it with a slightly blurred appearance). But when it was open on a computer with low performace, like a MAC or a laptop, the setting of the material was completely ignored, appearing completely reflective (like a mirror). To resolve this issue immediately, I changed the glossiness to 73, leaving the button more blurred than ideal, but worked!
I had open the model in three PCs (all opened properly), two laptops (material changed) and two MACs (material changed).
I wonder if it is normal these computers do not interpret the more accurate settings of materials or if this is only a bug in my model.