Spring Data MongoDB cannot reference the map's key property when array is the value type of a map

I'm trying to use Spring Data MongoDB Aggregation Framework Support to filter arrays based on specified conditions, but I could only get exception:

org.springframework.data.mapping.PropertyReferenceException: No property 10 found for type List! Traversed path: StudyRecord.channelRecords.

I guess what complicates the problem is that those arrays are value type in a map whose key is id of some other table.

The MongoDB document structure looks like this:

{
    "_id" : "dJ_o8070Sq2f8JqhYBZSjqDhP7Wk",
    "channelRecords" : {
        "10" : [ 
            {
                "startTime" : ISODate("2019-04-24T01:31:27.302Z"),
                "endTime" : ISODate("2019-04-24T02:36:27.302Z"),
                "_class" : "StudyRecordSingleDay"
            }, 
            {
                "startTime" : ISODate("2019-04-25T03:01:28.198Z"),
                "endTime" : ISODate("2019-04-25T04:01:28.198Z"),
                "_class" : "StudyRecordSingleDay"
            }
        ],
        "11" : [
            {
                "startTime" : ISODate("2019-04-23T03:01:28.198Z"),
                "endTime" : ISODate("2019-04-23T04:01:28.198Z"),
                "_class" : "StudyRecordSingleDay"
            }
        ]
    }
}

The corresponding POJO class is (class annotations omitted)

public class StudyRecord {

    @Id
    private String someId;

    private Map<Integer, List<StudyRecordSingleDay>> channelRecords;

}

To demonstrate that the aggregation works in mongo shell, here

db.studyRecord.aggregate([
    { $project: {
        "channelRecords.10": {
            $filter: {
                input: "$channelRecords.10",
                as: "record",
                cond: {$gte: ["$$record.studyTime",  ISODate("2019-04-01T23:14:19.000Z")]}
            }
        }
    } }
]);

The ProjectionOperation is constructed as below

project("_id")
.and(ArrayOperators.arrayOf("$channelRecords.10")
    .filter().as("record").by(
        new Document(
           "$gte", 
           Arrays.asList("$$record.startTime", LocalDateTime.parse("2019-04-24T01:31:27"))
        )
    ))
    .as("channelRecords.10")

I could not find specific sample code neither in Spring Data MongoDB reference documentation nor in official test classed.

I debugged some code and found that the problem seems to be caused by the array path reference ArrayOperators.arrayOf("$channelRecords.10"). Spring Data MongoDB seems to regard 10 as a property of channelRecords map's value type, which is List. Therefore, the exception No property 10 found for type List is raised

Would anyone shed light on my problem? Thanks!

Versions: spring-boot-starter-data-mongodb is used with Spring Boot Starter Parent version 2.1.4.RELEASE