How to reproduce it:
1. Open the attached project "1324728_issue.zip"
2. Open a Memory Profiler window (Menu Bar > Windows > Analysis > Memory Profiler)
3. Try to click on the "Compare Snapshots" button on the left side of the Memory Profiler window
4. Observe the "Compare Snapshots" button

Expected result: "Compare Snapshots" button is responsive to mouse events and gets a blue underline
Actual result: "Compare Snapshots" button is unresponsive to mouse events

Reproducible with: 1.0.0-preview.14 (2020.3.6f1, 2021.1.5f1), built-in UI Toolkit (2021.1.5f1, 2021.2.0a15)
Could not test with: 2018.4.34f1, 2019.4.25f1 (UI Toolkit is not introduced yet)

Notes:
- This issue can be fixed by going to Packages\com.unity.memoryprofiler-ui-tk-bug\Editor\UI\AnalysisWindow folder and opening a "MemoryUsageBreakdown.cs" file in Visual Studio. Uncomment line 144 and comment line 147 and save this file
- Could not reproduce with new project and UI Document
- UI gets broken when the width value is 1.0E+11 and a higher percentage

UPDATE 21/05/14:

The issue here was that an element ("memory-usage-bar__element__unknown") was set with a huge width value, leading to float calculation inaccuracies in the Yoga layout calculation due to difference in magnitude between parent and child areas. This caused the panel's world bounding box to be calculated as being outside of the panel area, causing user interactions in the panel to be rejected.

A fix has been implemented to prevent this from happening in the future and will be released soon. In general, it would be good practice to verify dynamically computed values to detect situations where they don't make sense.