Hi!
I've a similar problem (RTC v.5.02) and I tried all xpath possibilities to bypass the problem without any result. So, I have:

1. An enumerator defined as follow:

2. An HTTP Filtered Value Set as follow

XML Data Source: https://localhost:9443/Data/ufficio_richiedente.xml
Row XPath Expression: /xml/node[contains(./nomeBanca, "${it.gvb.customattribute.corporation.label}")]/ufficio
Column XPath expression: ./nomeBanca
Entry label format: ${0}

Apply filter string to values received from datasource = CHECKED
Ignore invalid SSL certificates = CHECKED

3. Ufficio_richiedente.xml as follow:

       <?xml version="1.0" encoding="UTF-8"?>
        <xml>
         <node> <nomeBanca>Name</nomeBanca>
    <codBanca>6</codBanca>
    <ufficio>6 - 0303 - NEW</ufficio>
  </node>
  <node>
    <nomeBanca>Name Space</nomeBanca>
    <codBanca>9</codBanca>
    <ufficio>9 - 1147 - NEW</ufficio>
  </node>
  <node>
    <nomeBanca>Name Space1</nomeBanca>
    <codBanca>2</codBanca>
    <ufficio>3 - 1117 - NEW</ufficio>
  </node>
</xml> 

When ${it.gvb.customattribute.corporation.label} input is “Name” the xpath match, instead when the input is “Name Space” or “Name Space1” there is no match and the dropdown shows loading label.

I also tried with:

1. Xpath tester --> it works properly
2. Using fixed value instead the variable, like /xml/node[contains(./nomeBanca, "Name Space")]/ufficio  --> it works properly

Any idea? 

 In target match user %20 as space. So, you will have: