Recruiting API works only sometimes (Zapier)

I use Zapier to link incoming applications from Typeform to Personio.

Since I couldn't get the Zapier integration to work with the Recruiting API, I had to work with a webhook in Zapier.

I followed the instructions from the Recruiting API doc but sometimes the transfer works and sometimes it doesn't. I couldn't see any pattern when it works and when it doesn't.

This is my JSON body:

{
"job_position_id": 12345,
"first_name": "Max",
"last_name": "Mustermann",
"email": "[email protected]",
"message": "Ausbildung im Bereich: ja",
"files": [
{
"original_filename": "filename.pdf",
"uuid": "123abc123abc",
"category": "other"
}
],
"attributes": [
{
"id": "phone",
"value": "0123456789"
},
{
"id":"available_from",
"value": "2001-01-01"
}
]
}

I don't know how to solve the problem. Is there any way to use the Recruiting API with Personio's Zapier integration?