Hi,
The issue you mentioned is unable to reproduce in our end, the processcmdkey is for the internal purpose of the dropdown calendar, so the text area works fine in our end over the DateTimePickerAdv. I have attached a sample with the UserControl on which we tried, please try to reproduce the issue in the sample or send us a minimal sample if possible, which shows the issue.
The sample is attached in the below location:
http://help.syncfusion.com/support/Tools.Windows/F93192/DateTimeKeyIssue.zipAlso please let us know the version of Essential Studio you use in your application, this will help us to check the issue in that version.
Regards,
Nirmal