Reproduction steps:
1. Open the attached project "IK_Bug.zip"
2. In the Hierarchy window select Stickman Gameplay -> Animation object
3. In the Menu bar click Window -> Animation -> Animation
4. In the Animation window select "Jump" animation
5. Observe the character's Animation state in the Scene View
6. In Animation view click Preview (with Play Mode disabled)
7. Observe the character's Animation state in the Scene View
8. Click Preview again (disable)
9. Observe the character's Animation state in the Scene View

Expected result: Character's Animation state before previewing the Animation and after is the same
Actual result: The character's Animation state after previewing has changed (hands are not aligned to the same position)

Reproducible with: 5.0.6 (2020.3.16f1), 6.0.4 (2021.1.17f1), 7.0.0-pre.2 (2021.2.0b7, 2022.1.0a5)
Could not test with: 5.0.6 (2019.4.29f1) - Character objects break due to downgrading the project

Notes:
1. The character's position can be reset (returned to the original state) by refreshing the Editor (deselecting and selecting the object again, minimizing/maximizing Unity Editor, or by clicking some of the buttons in the Unity Editor interface)
2. Does not reproduce in Play Mode