Yoni,

Curious… the default behavior of the Presets is for the adjustments to be added to your image, not to replace them. If you hold down the Option key (an instruction that pops up in the preview window when you’re looking at the different Presets), then it will replace all adjustments.

It will, however, always replace an adjustment that it uses in the preset. For example, the preset Quick Fixes > Brighten Shadows utilizes Enhance and Highlights & Shadows, so if you’ve already applied those adjustments, they will be replaced—there’s no way around this (and it’s an application enhancement I’ve requested—I want the option to add multiple instances of the same adjustment through Presets). However adjustments that it doesn’t use (such as Crop) should be left alone.

If that’s not what you’re seeing, please ensure that the Option key isn’t being inadvertently held down. If it’s not, try pressing it and see what happens; let’s see if that reverses the state.