createAsyncThunk: Error: addCase cannot be called with two reducers for the same action type

This happens because in my actions there is few AsyncThunks actions with the same typePrefix.

So it must have different names:

export const fetchCountries = createAsyncThunk(
  `getCountry`, //<------ this first argument (name) must be unique
  async (organizationId: string) => {

export const saveCountry = createAsyncThunk(
  `postCountry`,
  async ({ } => {})

In my case, the same error message was show, but it was a different mistake:

.addCase(setAddress.pending, (state, action) => {
    state.setAddressStatus = 'Pending';
})
.addCase(setAddress.fulfilled, (state, action) => {
    state.setAddressStatus = 'Fulfilled';  
})
.addCase(setAddress.fulfilled, (state, action) => { // I repeated fulfilled 
    state.getAddressesStatus = 'Rejected';
    console.error(action.error);
})
            

It took me some minutes to find the problem, may help someone.

On CreateAsycThunk you have mentioned both the string of the same name it should be like this

export const fetchCountries = createAsyncThunk(
  `country`, 
  async (organizationId: string) => {

export const saveCountry = createAsyncThunk(
  `saveCountry`,
  async ({ } => {})

const regions = createSlice({
  name,
  initialState,
  reducers: {},
  extraReducers: builder => {
    builder.addCase(fetchCountries.pending, isFetching);
    builder.addCase(fetchCountries.rejected, error);
    builder.addCase(fetchCountries.fulfilled, (state, action) => {});

    builder.addCase(saveCountry.pending, isFetching);
    builder.addCase(saveCountry.rejected, error);
    builder.addCase(saveCountry.fulfilled, (state, {payload}) => {});

createasyncthunk has two main parameters, one of type string and the latter callback function which has api and thunk as paramters. You are likely to be pardon if having a single asyncthunk in your slice, which has "" as data, but if you have two or more asyncthunks then checks will be made on each thunk, if two or more of them has similar "" or "identical" names then you will get disturbing error. "createAsyncThunk: Error: addCase cannot be called with two reducers for the same action type"