How to reproduce:
1. open the attached project
2. Open and run main scene
3. Check the Dropdown on the left that's being used inside a stencil-buffer using Mask for the expected result when using a dropdown
4. Try to open the middle Dropdown and notice how it gets cut off
5. Try to open the right-most Dropdown and notice how it doesn't open at all due to being placed near the bottom screen border

Not reproducible: 5.2.4p1