Hi Alomgir,
Thank you for your interest in Syncfusion product.
I am unable to reproduce this in GridGroupingControl FilterBar, when the custom has been selected in FilterBar. I have tried with sample, Also I have attached the video file in below link:
http://files.syncfusion.com/support/samples/Grid.Windows/Forums/GDBGFilter.zipPlease let me know with more details or send minimal sample if still face the issue.
Regards,
Lingaraj S.