Hi Sergy,
I am afraid that I am not able to reproduce the issue that you have mentioned here. Please refer the following steps that I tried to reproduce it:
1. Created a simple sample with GGC.
2. Enabled Ajax by placing the Grid inside an UpdatePanel.
3. Having Button and CheckBox as ItemTemplate.
4. Triggered Button click event and Checkbox's CheckedChanged event.
5. Bot the getting triggered with out any issues.
Please refer the sample from the below link, which illustrates this:
http://www.syncfusion.com/support/user/uploads/Sample_239d9b3d.zipPlease try like above, If still the issue exists could you please try reproduce the issue with the above sample and send back to us? so that we could find out the real cause of the issue and provide you a better solution.
Regards,
Raji