Hello Arfei,
Thank you for contacting us.
This appears to be an issue in
RadRibbonForm. I have logged it in our Public Issue Tracking System so you can track it and vote for it. We will address it in a future release. Here is the
link to the PITS item.
For the time being, you can try using the following workaround:
You might notice a thin black line next to the bottom border of the form as a result from this workaround. However, this is the only approach I can suggest by this moment.
Your Telerik points have been updated for bringing this issue to our attention.
Feel free to write back if you have any additional questions.
Greetings,
Ivan Todorov
the Telerik team