When using a DateTime? for input and a specific format, for example yyyy-MM-dd. If you just want to change the month part and type 03 the focus shifts to the start of the input and the month part gets replaced by MM.

Reproduce:

https://blazorrepl.telerik.com/QGYFEfPU52ceM2wL03

Select the month part and type 03 for example. If using a non nullable DateTime, this does not happen.

The picture says it all!