Multi-select Params not working via HTTP URL

Hi,

I am running JRS-Pro 6.3.0 on AWS.

I have created a report using Jasper Studio and added it to JSR manually by uploading the jrxml file.
I need to pass 3 parameters, so I have created 3 Input Controls in the report on JSR and named them same as the parameters names.
One of them is a multi-select list, so the corresponding param data type is set to java.util.List in jrxml. (I have also tried setting it to java.util.Collection.)

I tested this in Studio and everything is working fine.

Eventually, I am embedding this report as HTTP URL in a separate web app.
So I am passing parameters on the HTTP URL. I am getting error message "HTML response error code: 500".
My observation is that except multi-select param, all other params are working fine.

The URL looks like below:
http://<AWSIP>/jasperserver-pro/flow.html?_flowId=viewReportFlow&decorate=no&viewAsDashboardFrame=true&reportUnit=/organizations/org1/Reports/Report1&j_username=user1&j_password=user@123&USER_ID=1&USER_ID=2&USER_ID=3&START_DATE=2017-03-01&END_DATE=2017-03-05

Not sure what could be the problem.

Thank you,
Amit