The bug

Using the Spyglass and then pausing the game quickly in Singleplayer causes the Spyglass scope zoom animation to continue without decreasing the FOV until it finishes. Returning to the game cancels the animation and increases the FOV back to the specifications.

How to reproduce

1. Make sure to be in a Singleplayer world before reproduction.
2. Use a Spyglass by pressing the Right Button by default.
3. Quickly pause the game right after using the Spyglass.
   → The Spyglass scope animation continues as the FOV stops decreasing.

Possible fixes

The Spyglass scope animation should stop zooming in as the FOV stops decreasing to make more sense. The FOV may not stop decreasing as an alternate fix if the animation should continue like Fire and other animated blocks as the game pauses.