Java SDK Update metadata attribute on a file

Hi,

I've troubles updating a metadata attribute on a file.

I followed the instructions on the github site and on the documentation site.

BoxFile file = new BoxFile(api, "id");

file.updateMetadata(new Metadata().add("/foo", "bar"));

In my case:

BoxFile boxBestand = new BoxFile(api, bestandsId);

boxBestand.updateMetadata(new Metadata().add("/"+veld, waarde));

Tried:

BoxFile boxBestand = new BoxFile(api, bestandsId);

boxBestand.updateMetadata(boxBestand.createMetadata(template, "enterprise",  new Metadata().add("/"+veld, waarde));

And tried this method:

BoxFile boxBestand = new BoxFile(api, bestandsId);

Metadata metadata = new Metadata();
metadata = boxBestand.getMetadata(template, "enterprise");
metadata = metadata.replace("/"+veld, waarde);
boxBestand.updateMetadata(boxBestand.createMetadata(template, "enterprise", metadata));

All I get is 400 errors.

The API returned an error code [400 | bu1qqzggyxcgu1z4.034474d9889552d8bf4cf8604601c282d] schema_validation_failed - object instance has properties which are not allowed by the schema: ["retentiebeleid"]

Regards,

Marcel