Updating service fetch configuration in the form editor causes problems

[SilviaAmAm]

Product versie / Product version

2.4.2

Omschrijf het probleem / Describe the bug

Observed on Den Haag ACC environment.

The service fetch action had the following JSON:

{
  "component": "",
  "variable": "result",
  "formStep": "",
  "formStepUuid": null,
  "action": {
    "type": "fetch-from-service",
    "value": "1"
  }
}

And updating the service in the modal changed it to:

{
  "component": "",
  "variable": "result",
  "formStep": "",
  "formStepUuid": null,
  "action": {
    "type": "fetch-from-service",
    "value": "1"
  },
  "fetchConfiguration": {
    "existing": "9"
  }
}

But then upon saving the form, the initial JSON was not updated.

Stappen om te reproduceren / Steps to reproduce

No response

Verwacht gedrag / Expected behavior

No response

Screen resolution

None

Device

None

OS

None

Browser

No response

[SilviaAmAm]

Related: #3052