Thank you for writing.
We already have a couple reports for such an issue, however, we never got a scenario that allows us to reproduce it, thus we never managed to investigate it. If you manage to get such a scenario, please get back to us with it and we will investigate the reasons causing it.
Unfortunately, there is no easy way to rebuild your ribbon, so you can backup your form and restore it when this happens. Additionally, I would suggest using our latest version (if you are not already), where we introduced some fixes in the RibbonBar, hoping that they might be the reason for such a behavior.
Please excuse us for the introduced inconvenience.
the Telerik team