Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Create a new Terrain Layer Asset (Assets > Create > Terrain > Terrain Layer)
3. Assign any texture to the Mask Map
4. Click on the Channel Remapping dropdown's title
5. Observe the Inspector window

Actual results: The dropdown does not open

Expected results: The dropdown opens

Reproducible with versions: 6000.0.61f1, 6000.2.10f1, 6000.3.0b8, 6000.4.0a3

Tested on (OS): MacOS Silicon Sequoia 15.6.1, Windows 11

Notes:

• Other similar dropdowns in the Editor open when clicked on the title