To reproduce:
1. Open project
2. Open 'test' scene
3. Select 'Panel' gameobject in Hierarchy
4. In 'Content Size Fitter (Script)' component change 'Vertical Fit' to PreferredSize
5. Vertical Anchor of 'Panel' ('Stretch') is being changed to 'Bottom'
6. Disable 'Content Size Fitter (Script)' component
7. Change 'Anchor Preset' to 'Stretch/Stretch' (To preset in lower right corner)
8. Anchor Preset doesn't change to 'Stretch/Stretch'

Possible workarounds:
1. Remove disable 'Content Size Fitter (Script)' component from gameobject
2. Change 'Vertical Fit' to 'Unconstrained' in disabled 'Content Size Fitter (Script)' component