We are able to reproduce the reported issue (“ListBox returns string in the checkchange event argument”), we have confirmed this as a defect and logged an issue report for this. Please log on to our support website to check for further updates.
https://www.syncfusion.com/account/login?ReturnUrl=%2fsupport%2fdirecttrac%2fincidents
Please let us know if you have further queries.
Regards,
HariKrishnan