Reproduction steps:
1. Download and open the attached "UIToolkit Bug.zip" project
2. Select the "Pixel Cloud Shape Wizard Crown" game object
3. In the Inspector window, change the "Simulation Space" to "Custom"
4. Drag the "GameObject" game object into the "Custom Simulation Space" field
5. Move the particle system around the Scene view
Expected result: The particle system does not flicker/disappear
Actual result: The particle system flickers/disappears
Reproducible with: 2019.4.35f1, 2020.3.26f1, 2021.2.9f1, 2022.1.0b3, 2022.2.0a1