I am having a light/shadow problem since several days now on all my models.
Basically, I have "shadow rays" on all my models that I did not have previously. See my short video. Even models that were uploaded to Sketchfab months ago do show this now. As shown in the video, setting the Shadow Bias value from default (0.266) to >0.366 largely improves this problem.
But still I have running dark patches here and there as shown here on my small video here. Changing light rotation (light #2 especially) solves it localy but they appear somewhere else on the models.
What has been changed recently in the Skecthfab viewer ?
It's a bit scary to see these problems appearing on unmodified models...