I published this model yesterday, containing a couple of materials with opacity turned on: one of them uses the new Refraction mode (amber), the other using the usual Blending mode (floor).
I have noticed that after some indeterminate time/reason, I would load up my model and see that opacity has stopped working for the floor, like so:
Here’s what it looks like in the 3D settings (and should look like):
If I tweak the floor’s opacity and save the settings, the floor would be fixed again, but eventually the opacity problem returns. The refraction seems to stay unaffected though. I am on Firefox 58.0.2, if that helps. Let me know if I can provide any more information!