If already know keys why don’t use KV get and KV write by changing the document in SDK.
Simplified query. May not help your error
INSERT INTO Schedules(KEY x.id, VALUE x)
SELECT OBJECT_CONCAT(d, {"id":$newScheduleId, "scenarioId": $newScenarioId}) AS x
FROM Schedules AS d USE KEYS $oldScheduleId ;
One query sending more than one value as object
INSERT INTO Schedules(KEY x.id, VALUE x)
SELECT OBJECT_CONCAT(d, $obj.[META(d).id]) AS x
FROM Schedules AS d USE KEYS OBJECT_NAMES($obj);
$obj = {"oldScheduleId1":{"id":"newScheduleId1", "scenarioId": "newScenarioId1"},
"oldScheduleId2":{"id":"newScheduleId2", "scenarioId": "newScenarioId2"},
......
}