Reproduction steps:

# Open the user-attached project
# Open the “SampleScene” scene
# In the Hierarchy select Terrain GameObject
# In the Inspector for the Terrain component select the “Paint Trees” tab
# Move the mouse cursor over the Inspector window

Expected result: No visible flickering in the Inspector
Actual result: Flickering in the Inspector

Reproducible with: 3.0.2-preview.3 (2020.3.42f1), 4.0.3 (2021.3.14f1, 2022.1.23f1), 5.0.2 (2022.2.0b16, 2023.1.0a19)

Reproduced on: Windows 10

Note: The issue becomes more apparent when UI Scaling is more than 100% (Preferences → UI Scaling → Use custom scaling value). The editor sometimes can also throw DivideByZeroException, but the behavior is intermittent.