Unable to calculate route

Hello,

I'm getting an "Unable to calculate route" error with the following request:

http://www.mapquestapi.com/directions/v2/route?outFormat=xml&key=*****&f...

The odd thing is that if I swap from and to, it works.  Also, if I change the from address slightly - say from 5001 to 5002 - it also works.  Finally, the route works on mapquest.com.  Here's the full xml response:

<?xml version="1.0" encoding="UTF-8"?>
<response>
  <info>
    <statusCode>602</statusCode>
    <messages>
      <message>200 Unable to calculate route.</message>
    </messages>
    <copyright>
      <imageUrl>http://api.mqcdn.com/res/mqlogo.gif</imageUrl>
      <imageAltText>© 2017 MapQuest, Inc.</imageAltText>
      <text>© 2017 MapQuest, Inc.</text>
    </copyright>
  </info>
  <routeError>
    <errorCode>202</errorCode>
    <message></message>
  </routeError>
  <route>
    <sessionId></sessionId>
    <options>
      <shapeFormat>raw</shapeFormat>
      <generalize>-1.0</generalize>
      <maxLinkId>1</maxLinkId>
      <narrativeType>text</narrativeType>
      <stateBoundaryDisplay>true</stateBoundaryDisplay>
      <countryBoundaryDisplay>true</countryBoundaryDisplay>
      <sideOfStreetDisplay>true</sideOfStreetDisplay>
      <destinationManeuverDisplay>true</destinationManeuverDisplay>
      <avoidTimedConditions>false</avoidTimedConditions>
      <enhancedNarrative>false</enhancedNarrative>
      <returnLinkDirections>false</returnLinkDirections>
      <timeType>0</timeType>
      <routeType>FASTEST</routeType>
      <locale>en_US</locale>
      <unit>M</unit>
      <tryAvoidLinkIds></tryAvoidLinkIds>
      <mustAvoidLinkIds></mustAvoidLinkIds>
      <manmaps>true</manmaps>
      <drivingStyle>2</drivingStyle>
      <highwayEfficiency>22.0</highwayEfficiency>
      <useTraffic>false</useTraffic>
    </options>
    <mapState>
      <center>
        <latLng>
          <lat>0.0</lat>
          <lng>0.0</lng>
        </latLng>
      </center>
      <height>450</height>
      <width>675</width>
      <scale>0</scale>
    </mapState>
    <distance>0.0</distance>
    <time>0</time>
    <realTime>-1</realTime>
    <fuelUsed>0.0</fuelUsed>
    <formattedTime>00:00:00</formattedTime>
    <legs/>
    <hasTollRoad>false</hasTollRoad>
    <hasFerry>false</hasFerry>
    <hasHighway>false</hasHighway>
    <hasSeasonalClosure>false</hasSeasonalClosure>
    <hasUnpaved>false</hasUnpaved>
    <hasCountryCross>false</hasCountryCross>
    <hasBridge>false</hasBridge>
    <hasTunnel>false</hasTunnel>
    <locations>
      <location>
        <street>5001 Newport Coast Dr</street>
        <adminArea5 type="City">Irvine</adminArea5>
        <adminArea3 type="State">CA</adminArea3>
        <adminArea4 type="County">Orange</adminArea4>
        <postalCode>92603-0164</postalCode>
        <adminArea1 type="Country">US</adminArea1>
        <geocodeQuality>ADDRESS</geocodeQuality>
        <geocodeQualityCode>L1AAA</geocodeQualityCode>
        <dragPoint>false</dragPoint>
        <sideOfStreet>R</sideOfStreet>
        <displayLatLng>
          <latLng>
            <lat>33.633258</lat>
            <lng>-117.835675</lng>
          </latLng>
        </displayLatLng>
        <linkId>26446517</linkId>
        <type>s</type>
        <latLng>
          <lat>33.633258</lat>
          <lng>-117.835675</lng>
        </latLng>
      </location>
      <location>
        <street>1801 Park Court Pl</street>
        <adminArea5 type="City">Santa Ana</adminArea5>
        <adminArea3 type="State">CA</adminArea3>
        <adminArea4 type="County">Orange</adminArea4>
        <postalCode>92701-5000</postalCode>
        <adminArea1 type="Country">US</adminArea1>
        <geocodeQuality>POINT</geocodeQuality>
        <geocodeQualityCode>P1AAA</geocodeQualityCode>
        <dragPoint>false</dragPoint>
        <sideOfStreet>L</sideOfStreet>
        <displayLatLng>
          <latLng>
            <lat>33.750573</lat>
            <lng>-117.841221</lng>
          </latLng>
        </displayLatLng>
        <linkId>26363099</linkId>
        <type>s</type>
        <latLng>
          <lat>33.749882</lat>
          <lng>-117.841202</lng>
        </latLng>
      </location>
    </locations>
    <locationSequence>0,1</locationSequence>
    <computedWaypoints/>
  </route>
</response>

I've tried a number of different params, including ambiguities, doReverseGeocode, and maxRoutes.  Any help would be appreciated.