The bug is a subtle GUI glitch with the spyglass when swapping between no GUI and GUI using the F1 button.
What I expected to happen was:
There to be no animation when switching on the GUI with the telescope zoomed in.
What actually happened was:
When turning the GUI back on (with the F1 button) the spyglass displays the zooming in animation even though the screen is already zoomed in on.
Steps to Reproduce:
1. Take out spyglass.
2. Turn off GUI with F1.
3. Zoom in with spyglass using right mouse.
4. Turn back on GUI while still zooming with F1.
5. Observe zooming in animation, even though already zoomed in.