I have been encountering this bug for a long time and it hasn't been resolved yet.
Everytime you go back to edit a mirror feature, you aren't really able to edit the selections, neither add or exclude bodies. Even if you try to clear the previous selection and make a new one in the same feature, the feature only allows you to select entities once. After that, it doesn't allow you to select entities anymore. Kind of frustrates, because the only resolution for this becomes deleting the mirror feature and making a new one at the same history mark, which also results to you losing references of the mirror feature.
Effectively, this messes up with the whole idea of parametric modelling.
Fusion
