It almost appears like it's index of refraction hitting the hard normals of triangulated geometry. Have you tried rendering with glass set to auto smooth (Object Data Properties>Normals>Auto Smooth)? Turn the glass object off during render and see if distortion occurs. Give the glass a shiny reflective MatCap material and check if normals reflect oddly. Some modifiers that can help (depending on if you want sharp or smooth glass): 1. Weighted Normal 2. Edge Split. You typically use them separately.