How to reproduce:
1. Open the “AnimationSSTest.zip“ project
2. Select the “Weresnake@2HitCombo_A“ FBX in the Project Tab
3. In the Inspector, play the animation preview at the bottom
4. Unfocus the Editor (Click on another window)
5. Wait 1 minute
6. Observe the animation preview without focusing on the Editor

Expected result: Preview either plays at the same framerate as when the Editor was unfocused, or the preview stops playing altogether after step 4 (like in Game view during Play Mode)
Actual result: Preview starts and keeps gradually slowing down (reducing framerate)

Reproducible in: 6000.0.0b12, 6000.0.59f1, 6000.2.7f1, 6000.3.0b4, 6000.4.0a1
Not reproducible in: 6000.0.0b11

Reproduced on: Windows 11 Pro (24H2)
Not reproduced on: No other environment tested

Notes:
- The initial slowdown after unfocusing is expected, I believe
- If the Editor is focused on again, the Preview will start to play as usual, at the right framerate
- In Play Mode, the animated object stops altogether when the Editor is unfocused, so it’s only the Inspector preview that is affected