The preview of a develop preset when hovering over it in the Presets panel is incorrect when the preset contains IncrementalTemperature and IncrementalTint values and the photo being edited is raw. To reproduce:
1. Open a non-raw in Develop and change Temp and Tint to +20.
2. Save a preset "Temp/Tint" with just White Balance checked.
3. Open a raw in Develop.
4. Hover the mouse over Temp/Tint and observe the change to the photo.
5. Click on Temp/Tint and observe there isn't any additional change to the photo (as expected).
6. Move the mouse pointer over the photo. Observe that the photo colors noticeably change.
7. Repeatedly move the mouse pointer back to over the Temp/Tint preset and then back over the photo and observe the change in colors.
Here's an example:
Develop Loupe view with mouse hovering over Temp/Tint preset:
Develop Loupe view after applying Temp/Tint preset with mouse over photo:
Tested on LR 8.4.1 / Mac OS 10.14.6 and Windows 10.