When there is ice behind stained glass it will always visually bug out after a while. When you first join the world it will start off fine but as you play you notice weird spots where it looks like the ice has completely disappeared, become lines, or smaller blocks that aren't connected. This bug has been happening for a while now and it ruins the look of windows with the ice behind it for the effect.
Please provide some additional screenshots or videos of this issue occurring whilst the F3 Debug screen is enabled.