Django multiple formsets of the same inline model

I have a model structure that lets the user define a page.

The code below shows a subset of it, and while I'm having no problem displaying the form with the formsets, I'm having trouble saving it, and then displaying it again.

Models.py

class Entity(models.Model):
    title       = models.CharField(max_length=50)

class ValueDefinition(models.Model):
    title       = models.CharField(max_length=50)   
    entity      = models.ForeignKey("Entity", null=True)
    order       = models.PositiveSmallIntegerField(default=0)

class Value(models.Model):
    value_definition    = models.ForeignKey("ValueDefinition")
    is_default          = models.BooleanField(default=False)  
    value_type          = models.CharField(max_length=50)
    char_value          = models.CharField(max_length=200, null=True, blank=True)
    integer_value       = models.IntegerField(null=True, blank=True)
    boolean_value       = models.BooleanField()

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As you can see I have: Entity -> ValueDef -> Value. With Foreign Keys upstream. Obviously I took out many more fields and left in the fields that will let you get the idea.

Problem is: I want to display, as a form, a series of entities, and their related Values. Of course the whole page is much more complex, but here is the relevant piece of code of the View:

Views.py:

def my_view(request, page)

    # some more code here...

    ValueInlineFormSet = inlineformset_factory(ValueDefinition, Value, ValueForm, extra=0)

    for entity in page.entities:
        vdef = entity.valuedefinition_set.first()
        if vdef:
            prefix = 'value_set-%s' % entity.pk
            if request.method == 'POST':
                formset = ValueInlineFormSet(request.POST, instance=vdef, prefix = prefix)
                if formset.is_valid():
                    formset.save()
            else:
                formset = ValueInlineFormSet(instance=vdef, prefix = prefix)

            entity.values_formset = formset

    return render(request, 'myapp/page.html', {'page': page})

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So now is the tricky part. Everything looks fine without the POST part. Meaning all the entities, where every entity has its Values inline formset - all are rendered properly. My problem is getting the relevant formset from the request.POST. When I call ValueInlineFormSet(request.POST, ...) I get back the full set of formsets, which includes all formsets of all entities! Then what happens is that the values are not saved, and obviously, the page doesn't look the same.

I intentionally didn't include the page template in order not to make things more complicated than they are (and I don't think it's really relevant), but let me know if you think it's relevant for the complete picture.

The HTML renders:

A form
Inside the form - loop over entities
inside an entity - loop the values formset
inside a form - display it's fields (django form, not html form!)
Thanks.