To recreate:

• Create a service, add a VFC
• Add an input to the service
• Set the value of a property of the VFC using a custom function
  • Add two values
    • string value: abc
    • expression value: get_input, selecting the input you created above
• Export the service
• Import the service
• Try to edit the property in the imported service - the checkbox is disabled and therefore the value cannot be edited
• Only seems to happen with get_input, no problem seen for get_property