Get Returns: Key 'returnReason' is missing in data array or is not a string

[DangerLifter]

In ReducedReturnItem.php line 195:

[InvalidArgumentException]
Key 'returnReason' is missing in data array or is not a string

Exception trace:
() at app/vendor/bol-com/retailer-api/src/Model/Rma/ReducedReturnItem.php:195
BolCom\RetailerApi\Model\Rma\ReducedReturnItem::fromArray() at app/vendor/bol-com/retailer-api/src/Model/Rma/ReturnItemList.php:53
BolCom\RetailerApi\Model\Rma\ReturnItemList::fromArray() at app/vendor/bol-com/retailer-api/src/Handler/Rma/GetAllReturnsHandler.php:59
BolCom\RetailerApi\Handler\Rma\GetAllReturnsHandler->__invoke() at app/vendor/bol-com/retailer-api/src/Infrastructure/MessageBus.php:111

Data from API:
Array
(
[rmaId] => XXX
[orderId] => XXX
[ean] => XXX
[quantity] => 0
[registrationDateTime] => 2019-10-22T09:54:14+02:00
[fulfilmentMethod] => FBB
[handled] => 1
[handlingResult] => RETURN_RECEIVED
[processingResult] => ACCEPTED
[processingDateTime] => 2019-10-22T09:54:20+02:00
)