You may notice that tools like Edit Collider on colliders or Edit Probes on light probes do not work. This is due to an internal Unity bug where only the first loaded inspector in your layout can use these buttons.
The report is filed here, but Unity has decided to postpone the issue indefinitely. We are trying to get Unity to re-prioritize the issue as it has been shelved since 2014.
Status: Unity bug, fixed in 2019.4. Issue Tracker Link
When opening the inspector popup on a sub-asset, that is anything within an asset's foldout in the Project window (e.g. sprites from textures, meshes from models, etc.), the popup for the root asset is shown instead. This is due to the limited API hooks that Unity gives us to integrate with the project window. Regardless of the item selected, we only get the GUID of the root asset, so we cannot target the sub-asset accurately.
Status: Unity limitation.
We noticed general instability in Mac OS X, where Peek can seemingly cause the editor to crash. However, the crash logs don't point to anything related to Peek, so our educated guess is that something used within our GUI libraries is failing in the OpenGL or Metal rendering engines used on the OSX editor.
If you have any way of consistently reproducing the crash, please let us know so we can file a more accurate report. In the mean time, we ask you to please send your Unity crash reporter logs when Unity crashes in order to help Unity isolate and fix the issue.
Status: Investigating, cannot reliably reproduce, has not been reported for months.