I am trying to make a simple scene where there is a glass bottle with some liquid inside of it. To make the liquid, I just sliced a sphere in half, gave it a volume and glass shader, and put it inside the bottle.
When I rendered it (Blender Cycles 2.83 Beta), I noticed some very strange things appearing in the liquid. (Look below)
Here is the .blend- before discovering this issue, I wanted to replace the liquid with fluid simulation. The objects that you won't need to investigate should be hidden from view.
Here is a closer view with the problems labeled:
As you can see, the borders of the liquid inside the glass have a strange "pixelated" look that does not match the resolution of the image, nor does it look realistic.
For lighting, I am using a completely black environment. I added a red and blue light next to each other to use as the main lighting.
I can also guarantee that there are no intersecting surfaces. I have no idea why this is happening. I also couldn't find any other people who have experienced a similar issue.