We need a way to disable the _step function (kendo.web.js) from being run whenever keying up or down in a nullable NumericTextBox grid column. Without this, moving between cells is setting the value of the cell being stepped out of to zero despite no text/numerical input. Our workaround was to override the Kendo JS to skip the majority of the _step logic by checking for whether spinners were disabled:

if(that.options.spinners === false) {
	return;
}

See support ticket logged for further information and code/video example: https://www.telerik.com/account/support-tickets/view-ticket/1408355