[rasa 2] why a slot extracts an array of string, but not a string which is supposed to be

The log below shows the rasa extracts bothe startLocName and endLocName successfully ({‘startLocName’: ‘津市’, ‘endLocName’: ‘洞庭湖’}), however, I’ve no idea why it then extracts startLocName and endLocName again and makes them as two arrays of string ({‘startLocName’: [‘津市’, ‘津市’], ‘endLocName’: [‘洞庭湖’, ‘洞庭湖’]}).

It seems the extraction runs twice for each slot, and add the two runs as an array together. It’s very wierd to me. I never met this kind of situation before.

Any tips or help will be appreciated!

btw, the chinese characters is not important, just ignore them.

2020-10-15 17:26:19 DEBUG    rasa.core.processor  - Current slot values:
        endLocName: None
        feedback_message: None
        feedback_value: None
        multiLocName: None
        requested_slot: None
        startLocName: None
2020-10-15 17:26:20 DEBUG    rasa.nlu.selectors.response_selector  - Adding following selector key to message property: ask_faq
2020-10-15 17:26:20 DEBUG    rasa.core.processor  - Received user message '从津市到洞庭湖的洪水传播' with intent '{'id': -2976797603698282810, 'name': 'query_flood_propagation', 'confidence': 0.9999997615814209}' and entities '[{'entity': 'startLocName', 'start': 1, 'end': 3, 'confidence_entity': 0.9996120391825801, 'role': 'from', 'confidence_role': 0.9999874781636586, 'value': '津市', 'extractor': 'CRFEntityExtractor'}, {'entity': 'endLocName', 'start': 4, 'end': 7, 'confidence_entity': 0.9991268799217391, 'role': 'to', 'confidence_role': 0.9997706526351009, 'value': '洞庭湖', 'extractor': 'CRFEntityExtractor'}, {'entity': 'startLocName', 'start': 1, 'end': 3, 'confidence_entity': 0.999981164932251, 'role': 'from', 'confidence_role': 0.999974250793457, 'value': '津市', 'extractor': 'DIETClassifier'}, {'entity': 'endLocName', 'start': 4, 'end': 7, 'confidence_entity': 0.9999885559082031, 'role': 'to', 'confidence_role': 0.9999841451644897, 'value': '洞庭湖', 'extractor': 'DIETClassifier'}]'
2020-10-15 17:26:20 DEBUG    rasa.core.processor  - Current slot values:
        endLocName: 洞庭湖
        feedback_message: None
        feedback_value: None
        multiLocName: None
        requested_slot: None
        startLocName: 津市
2020-10-15 17:26:20 DEBUG    rasa.core.processor  - Logged UserUtterance - tracker now has 6 events.
2020-10-15 17:26:20 DEBUG    rasa.core.policies.memoization  - Current tracker state [{}, {'user': {'intent': 'query_flood_propagation', 'entities': ('startLocName', 'endLocName')}, 'prev_action': {'action_name': 'action_listen'}}]
2020-10-15 17:26:20 DEBUG    rasa.core.policies.memoization  - Launch DeLorean...
2020-10-15 17:26:20 DEBUG    rasa.core.policies.memoization  - Current tracker state [{}, {'user': {'intent': 'query_flood_propagation', 'entities': ('startLocName', 'endLocName')}, 'prev_action': {'action_name': 'action_listen'}}]
2020-10-15 17:26:20 DEBUG    rasa.core.policies.memoization  - There is no memorised next action
2020-10-15 17:26:20 DEBUG    rasa.core.policies.rule_policy  - Current tracker state: [{}, {'user': {'intent': 'query_flood_propagation', 'entities': ('startLocName', 'endLocName')}, 'prev_action': {'action_name': 'action_listen'}}]
2020-10-15 17:26:20 DEBUG    rasa.core.policies.rule_policy  - There is a rule for the next action 'flood_propagation_form'.
2020-10-15 17:26:20 DEBUG    rasa.core.policies.ensemble  - Predicted next action using policy_2_RulePolicy
2020-10-15 17:26:20 DEBUG    rasa.core.processor  - Predicted next action 'flood_propagation_form' with confidence 1.00.
2020-10-15 17:26:20 DEBUG    rasa.core.actions.forms  - Activated the form 'flood_propagation_form'.
2020-10-15 17:26:20 DEBUG    rasa.core.actions.forms  - Validating pre-filled required slots: {'startLocName': '津市', 'endLocName': '洞庭湖'}
2020-10-15 17:26:20 DEBUG    rasa.core.actions.action  - Calling action endpoint to run action 'validate_flood_propagation_form'.
2020-10-15 17:26:20 DEBUG    rasa.core.actions.forms  - Validating user input 'UserUttered(text: 从津市到洞庭湖的洪水传播, intent: {'id': -2976797603698282810, 'name': 'query_flood_propagation', 'confidence': 0.9999997615814209}, entities: [{'entity': 'startLocName', 'start': 1, 'end': 3, 'confidence_entity': 0.9996120391825801, 'role': 'from', 'confidence_role': 0.9999874781636586, 'value': '津 市', 'extractor': 'CRFEntityExtractor'}, {'entity': 'endLocName', 'start': 4, 'end': 7, 'confidence_entity': 0.9991268799217391, 'role': 'to', 'confidence_role': 0.9997706526351009, 'value': '洞庭湖', 'extractor': 'CRFEntityExtractor'}, {'entity': 'startLocName', 'start': 1, 'end': 3, 'confidence_entity': 0.999981164932251, 'role': 'from', 'confidence_role': 0.999974250793457, 'value': '津市', 'extractor': 'DIETClassifier'}, {'entity': 'endLocName', 'start': 4, 'end': 7, 'confidence_entity': 0.9999885559082031, 'role': 'to', 'confidence_role': 0.9999841451644897, 'value': '洞庭湖', 'extractor': 'DIETClassifier'}])'.
2020-10-15 17:26:20 DEBUG    rasa.core.actions.forms  - Extracted '['津市', '津市']' for extra slot 'startLocName'.
2020-10-15 17:26:20 DEBUG    rasa.core.actions.forms  - Extracted '['洞庭湖', '洞庭湖']' for extra slot 'endLocName'.
2020-10-15 17:26:20 DEBUG    rasa.core.actions.forms  - Validating extracted slots: {'startLocName': ['津市', '津市'], 'endLocName': ['洞庭湖', '洞庭湖']}
2020-10-15 17:26:20 DEBUG    rasa.core.actions.action  - Calling action endpoint to run action 'validate_flood_propagation_form'.
2020-10-15 17:26:21 DEBUG    rasa.core.actions.forms  - Deactivating the form 'flood_propagation_form'
2020-10-15 17:26:21 DEBUG    rasa.core.processor  - Action 'flood_propagation_form' ended with events '[<rasa.shared.core.events.ActiveLoop object at 0x7f40fc330a90>, <rasa.shared.core.events.SlotSet object at 0x7f409c7aa390>, <rasa.shared.core.events.SlotSet object at 0x7f409c7aa550>, <rasa.shared.core.events.SlotSet object at 0x7f409c7aa2e8>, <rasa.shared.core.events.SlotSet object at 0x7f409c7aa780>, <rasa.shared.core.events.SlotSet object at 0x7f409c77a390>, <rasa.shared.core.events.ActiveLoop object at 0x7f40fc330b00>]'.