Why is my dynamic dropdown not updating using selectFirstChoice and token unset?

[dflodstrom]

I have a dashboard with dynamically populated dropdown inputs. Selecting input A sets token_A that the input B relies on for its populating search. I used + to unset token_B when the selection in input A changes and this works just fine unless I reload the browser after I've made my selection; if I do this token_B resets but the first option is not selected.

Here is input A (A list of available Datamodels):

<input type="dropdown" token="data_model" searchWhenChanged="false">
      <label>Data Model</label>
      <search>
        <query>| rest /services/datamodel/model | search eai:acl.app!=search | table displayName title eai:acl.app | sort displayName</query>
      </search>
      <fieldForLabel>displayName</fieldForLabel>
      <fieldForValue>title</fieldForValue>
      <change>
        <unset token="form.root_object_name"></unset>
      </change>
    </input>

Here is input B (Datamodel Root Object Name):

<input type="dropdown" token="root_object_name" searchWhenChanged="true">
      <label>Root Object Name</label>
      <selectFirstChoice>true</selectFirstChoice>
      <fieldForLabel>object_name</fieldForLabel>
      <fieldForValue>object</fieldForValue>
      <search>
        <query>| datamodel $data_model$ | spath | rename "objects{}.displayName" as object_name "objects{}.objectName" as object | table object | mvexpand object | head 1</query>
        <earliest>-24h@h</earliest>
        <latest>now</latest>
      </search>

I've read questions that lead me to a solution but it doesn't seem to work when I reload my dashboard. I'm using Splunk 6.5.2.