Yes we are able to reproduce the issues with a MVVM architecture. I am afraid that RadNumericUpDown currently does not support databinding of its NumberFormatInfo, and thus you will have to write some code-behind logic in your View that formats the control the way you want it. We understand that this is a shortcoming and we will do our best to get rid of it as soon as possible. Until then, I apology for this inconvenience.
If you have any further questions, please get back to us.
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