Hi, not sure if that happens only in latest build, but here’s what we have - wrong reflection with reflection glossiness below 1 and refraction enabled.
Yeah, it’s probably one more light transport issue: https://coronarenderer.freshdesk.com/support/solutions/articles/5000516180-known-bugs-and-limitations
Does enabling caustics fix this instantly?
yes, caustics fix this, but I don’t think that it’s a good option to enable caustics for each of such materials in scene or tricking with multilayered material.
I did a lot of renders with frosted glass and don’t remember such behavior earlier (or may be I didn’t noticed that).
I think it must have been there since at least a few versions. We are aware of this issue, and we know this may be often serious, so the fix is planned. This is however a very complex thing to fix, so please allow our developers some time for this.