Expense Report Update custom field

[bdbais]

I'm trying to update a custom field, but I receive everytime error 500.

I'm following api documentation but in this case is very abstract:

PUT APIhost (emea)
/api/v3.0/expense/reports/D69511FA9B544B528708?user=dummy@example.com

body:

{
"Custom17":"1119"
}

Response:

Internal Server Error2022-04-28T12:38:1503DE59EC-3E49-4964-BEAD-037D041FEA4A

I've tried various formats like
{
"ID": "D69511FA9B544B528708",
"Custom17":"1119"
}

or

{
"Custom17": { ""value" : "1119" }
}

but nothing.

there is a way to massive update custom colums of a report header ?

thx