I am logging the decimal incell editing issue in the following page: https://feedback.telerik.com/blazor/1417392-onupdate-does-not-fire-in-incell-edit-mode-for-decimal-fields.

On the error with filtering - this can happen if a column does not have a field defined, or the field is a composite field, the grid can only filter/sort primitive types. For complex types, they need to implement their own comparers, or you should only put the needed fields in the view model the grid is bound to. Here's this error treated in more detail: https://feedback.telerik.com/blazor/1408650-column-sorting-breaks-under-subclassing-scenarios. Is this what you have? If not, I'd suggest opening a support ticket where you can send me the reproducible.

I moved this to the portal so it can get fixed. Here's the new URL: https://feedback.telerik.com/blazor/1416617.

The only workaround I can offer for the moment is to us the "inline" editing mode.
With Preview7 when event callbacks get fixed for generic components, perhaps you would be able to hook to the ValueChanged of a numeric textbox defined in a custom editor and update the actual data source, but for the time being this isn't possible because of this issue.