Hello guys, ive created this image to explain better the errors we encountered on this matter, simple glass material works fine but on blend with standard corona material the shadows got wierd, on the 3rd sphere its a multi sub object with 2 ids material son instance, no problems but if you decide to copy the material (not instance just copy) on the seccond slot you get a refraction error, hope this helps.
Version of corona A7.1 final