I am having the same problem but :value didn’t help. Can anyone help me please???
I have two errors when i click checkboxes:

1. [Vue warn]: Error in callback for watcher “function () { return this._data.$$state }”: “Error: [vuex] do not mutate vuex store state outside mutation handlers.”
2. warn @ vue.runtime.esm.js?2b0e:619 Error: [vuex] do not mutate vuex store state outside mutation handlers.