ASP.NET MVC ViewModel is null on Post Back - sometimes - asp.net-mvc-4

Question

depending on my input in an HTML form (6 or 6.5 - or in general, integer VS float) I get or don't get the following exception (it works with int and doesn't work with float):
The model item passed into the dictionary is null, but this dictionary requires a non-null model item of type 'System.Boolean'.
The ViewModel of my View is null and the problem gets visible in a custom template which expects a bool value, but gets null instead. We use ASP.NET MVC 4 with .Net 4.0, C# and Razor Templates.
After several hours debugging I came to the following conclusion(s):
Post Form-Data are identical (except the one property which is different, but still look correct)
The execution order is somehow weirdly different:
for int I get Application_BeginRequest->Filter which runs through my attributes->Action->View Rendering OR Redirect (everything Normal)
for float I get Application_BeginRequest->Filter which runs through my attributes->View Rendering->END WITH AN EXCEPTION and Empty ViewModel
I have checked it dozen times -> If I pass float the View somehow gets rendered without any Action (which I would have seen) to be executed (and of course the breakpoints were the same all the time). Unfortunately I couldn't see anything in the StackTrace anymore once the View got rendered.
the ViewModel of my View is:
public class JabCommonViewModel
{
public int JAB_ID { get; set; }
[UIHint("Checkbox")]
public bool JAB_gesperrt { get; set; }
[UIHint("Checkbox")]
public bool JAB_Kontrolliert { get; set; }
public int e001 { get; set; }
public string e002 { get; set; }
public int e005 { get; set; }
[UIHint("Checkbox")]
public bool e013 { get; set; }
public bool e014 { get; set; }
public short? e015 { get; set; }
public bool? e149 { get; set; }
public int? e649 { get; set; }
public int? e310 { get; set; }
public int? LastJabe311 { get; set; }
public int jabIdE013 { get; set; }
public int jabIdPrev { get; set; }
public int updCnt { get; set; }
public int checks { get; set; }
public bool calculateInEur { get; set; }
public FormViewModel AktivaPassiva { get; set; }
public FormViewModel GuV1GuV2 { get; set; }
public FormViewModel GuV3 { get; set; }
public ActsFormViewModel ActsForm { get; set; }
public CommonDataViewModel CommonDataForm { get; set; }
public CompanyHeadViewModel CompanyHeadForm { get; set; }
public FacilitiesOverviewModel FacilitiesOverview { get; set; }
}
public class FormViewModel
{
public string ShowAllCaption { get; set; }
public string HideAllCaption { get; set; }
public string CurrentCaption { get; set; }
public string PreviousCaption { get; set; }
public bool HasPreviousData { get; set; }
public IEnumerable<FieldViewModel> Fields { get; set; }
public FormViewModel()
{
Fields = new FieldViewModel[0];
}
}
public class FieldViewModel
{
public string Name { get; set; }
public string Title { get; set; }
public object Value { get; set; }
public bool IsDisabled { get; set; }
public bool IsCollapsible { get; set; }
public bool IsSpecialCase { get; set; } // used currently to expand/collapse groups on second level
public FieldViewModel Previous { get; set; }
public Category DataCategory { get; set; }
public IEnumerable<FieldViewModel> Related { get; set; }
public FieldViewModel()
{
Related = new FieldViewModel[0];
}
public FieldViewModel(string name, string title, object value, bool isDisabled, Category dataCategory = Category.None, bool isCollapsible = true)
{
Name = name;
Title = title;
Value = value;
IsDisabled = isDisabled;
DataCategory = dataCategory;
IsCollapsible = isCollapsible;
Related = new FieldViewModel[0];
}
}
....
The Post-Back Action is
public ActionResult Edit(JAB2 jab)
{
ComponentFactory.Logger.Debug("Edit with JAB2");
....
}
public class JAB2 : JAB
{
public int jabIdE013 { get; set; }
public JAB LastJab { get; set; }
public int checks { get; set; }
}
public class JAB : BaseModel
{
public JAB()
{
}
public bool e116 { get; set; }
public bool e117 { get; set; }
public bool e118 { get; set; }
public bool e119 { get; set; }
public bool e120 { get; set; }
public bool e121 { get; set; }
public bool e122 { get; set; }
public bool e123 { get; set; }
public bool e124 { get; set; }
public bool e125 { get; set; }
public short? e126 { get; set; }
... /* 100 more properties */ ...
[LocalizedDisplayName("e751", NameResourceType = typeof(Resources.ModelPropertyNames))]
public float? e751 { get; set; } /* the property which works as int but not as float */
}
The Post-Back is actually to the link
/JAB/Edit/
Still the correct method get's executed when e751 (the special property) has an integer value.
Also we use the autoNumeric-JavaScript Plugin on that field. Also we use the plugin with other fields but so far found the error only with this one. As well, we have one Workstation where we aren't able to reproduce the error so it occurs on 2 out of 3 workstations + test server.
So far, nothing I've found explains the fact that it works sometimes.
Thank you very much for taking the time and reading my post.
Do you have any Ideas what could be wrong or what I could check?