It seems this issue is also affecting other controls which implement the ValueChanged event. I have had the same issue with DropDownLists, NumericTextBox and a few other controls too. It also seems that calling StateHasChanged() seems to disable all further change events on a particular control. @bind-Value works first time only and only updates the underlying variable once. ValueChanged also has the same issue, so for my NumbericTextBox I tried ValueChange - see below. If you put a breakpoint on the "AssignmentID=...." line it will break every time. If you uncomment the StateHasChanged(); line, it will break the first time you change the value, but never again after that. As I stated earlier, this affects DropDownList and other controls as well.
<EjsNumericTextBox TValue="int?" Format="#" ShowSpinButton="false" Placeholder="Assignment ID" FloatLabelType="FloatLabelType.Always" Value="@AssignmentID">
<NumericTextBoxEvents TValue="int?" ValueChange="AssignmentIDChanged" />
public int? AssignmentID;
protected void AssignmentIDChanged(Syncfusion.EJ2.Blazor.Inputs.ChangeEventArgs args)
AssignmentID = (int?)(args.Value == 0 ? (double?)null : args.Value);