Thanks for contacting us and for reporting this issue.
Could you please share with us more details on the case since I was not able to reproduce the any issues related with the drag and drop functionality of RadForm.
What I did was:
1. Created a RadForm and added a RadGridView control on the form.
2. Subscribed for the OnDragEnter, OnDragDrop, OnDragLeave, OnDragOver events.
3. Peformed some tests.
Everything seems to work as expected here.
Could you send us a simple Windows Forms application that we can use to reproduce the case so that we can investigate the reason for the undesired behavior and hopefully provide you with solution.
Please note that you will have to open a new support ticket in order to be able to attach files.
Thanks for your time.
I look forward to receiving the details requested.
All the best,
the Telerik team