Query parameters of GET request are cut up to the last value if Spring Boot app deployed as AWS lambda function

I'm sending the following request to Spring Boot application deployed as AWS lambda function:

GET https://my-dev-host.com/fdx/v6/accounts?accountIds=confUser_1&accountIds=confUser_2&accountIds=confUser_3&accountIds=confUser_4&offset=1&limit=3
Authorization: Bearer ....
Accept: application/json
Accept-Charset: UTF-8
Content-Type: application/json

But int the log I see that only the last accountId is actually arrives into controller:

Modified request:
{
  "multiValueQueryStringParameters": {
    "accountIds": [
      "confUser_4"
    ],
    "limit": [
      "3"
    ],
    "offset": [
      "1"
    ]
  },
  "queryStringParameters": {
    "accountIds": "confUser_4",
    "limit": "3",
    "offset": "1"
  },
  "multiValueHeaders": {
    "accept": [
      "application/json"
    ],
    "accept-charset": [
      "UTF-8"
    ],
    "accept-encoding": [
      "br, deflate, gzip, x-gzip"
    ],
    "authorization": [
      "Bearer ..."
    ],
    "content-type": [
      "application/json"
    ],
    "host": [
      "my-dev-host.com"
    ]
  },
  "headers": {
    "accept": "application/json",
    "accept-charset": "UTF-8",
    "accept-encoding": "br, deflate, gzip, x-gzip",
    "authorization": "Bearer ...",
    "content-type": "application/json",
    "host": "my-dev-host.com"
  },
  "pathParameters": {},
  "httpMethod": "GET",
  "stageVariables": {},
  "path": "/fdx/v6/accounts",
  "isBase64Encoded": false,
  "requestSource": "ALB"
}

I've tried to modify request as

GET https://my-dev-host.com/fdx/v6/accounts?accountIds=confUser_1&,confUser_2,confUser_3,confUser_4&offset=1&limit=3
Authorization: Bearer ....
Accept: application/json
Accept-Charset: UTF-8
Content-Type: application/json

But still no luck.

Here is the API of my controller:

@RequestMapping(
        method = RequestMethod.GET,
        value = "/accounts",
        produces = {"application/json"}
)
ResponseEntity<Object> searchForAccounts(
        @Parameter(name = "accountIds", description = "Comma separated list of account ids", in = ParameterIn.QUERY) @Valid @RequestParam(value = "accountIds", required = false) List<String> accountIds,       
        @Parameter(name = "offset", description = "Opaque cursor used by the provider to send the next set of records", in = ParameterIn.QUERY) @Valid @RequestParam(value = "offset", required = false) String offset,
        @Parameter(name = "limit", description = "Number of elements that the consumer wishes to receive. Providers should implement reasonable default and maximum values", in = ParameterIn.QUERY) @Valid @RequestParam(value = "limit", required = false) Integer limit
);

I believe the way API gateway maps the query parameters you need to comma separate your accountIds. Aka https://my-dev-host.com/fdx/v6/accounts?accountIds=confUser_1,confUser_2,confUser_3,confUser_4&offset=1&limit=3