How to reproduce:
1. Open any project with Cinemachine installed
2. In a "Cinemachine Camera" Component observe the dropdown menu field on the right of the Lens Vertical FOV field
3. Click on the field and select either option to create a preset Asset
4. Add a Preset by clicking the "+" button, a new Preset will be created with the values of the last one in the list
5. Rename this preset to whatever
6. Now select the GO with the "Cinemachine Camera" attached
7. In the Presets field select your renamed Preset
8. Select your Preset again

Actual result: By default, the Preset dropdown menu has no indication of what it is other than a tooltip.
When you select your custom Preset that has the same value as the default one, the default one is selected instead of the one the user made.
If you try and select your Preset again, the Presets dropdown menu becomes empty.

Expected result: By default, the Preset dropdown menu has an apparent indication of what it is, perhaps the field has "Presets" written.
When you select your custom Preset that has the same value as the default one, yours is selected instead
If you try and select your Preset again, the Presets dropdown menu still shows your Preset

Reproducible with: 3.0.0-pre.1, 3.0.0-pre.7