Saving fail, ending with 'ManagementForm data is missing or has been tampered with'

[jerom-dev]

Hello I'm struggling with this since some time now, i don't manage to save any nested inline :(
I have installed the django-nested-admin-3.3.2

I have three level inlines (but it failed also with only 2)

First save fail like if there is an error in the form, and it removes the third level of nested inline
If i try to save a second time from this altered form i get the error 'ManagementForm data is missing or has been tampered with'

I don't know what i'm doing wrong, or what i can do to debug this.

in my settings.py
INSTALLED_APPS = [ ... 'my app', 'nested_admin', 'django.contrib.admin', ]

In my admin.py i have

class StratOpenOrderInline(nested_admin.NestedTabularInline):
    model = StratOpenOrder

class StratMainOrderInline(nested_admin.NestedStackedInline):
    model = StratMainOrder
    inlines = [StratOpenOrderInline]

@admin.register(Strategy)
class StrategyAdmin(nested_admin.NestedModelAdmin):
    inlines = [StratMainOrderInline]

in StratMainOrder.py

class StratMainOrder(models.Model):
    id_strategy= models.ForeignKey(Strategy, on_delete=models.CASCADE)
...

in StratOpenOrder.py

class StratOpenOrder(models.Model):
    id_strat_main_order= models.ForeignKey(StratMainOrder, on_delete=models.CASCADE)
...

[jerom-dev]

Now i manage to avoid the error 'ManagementForm data is missing or has been tampered with' playing with the import orders
but the form is still not saving any data :(

[jacobjove]

I also see this error often. It seems to happen when a form is left open for too long (overnight, for example) and then submitted.

The error only happens with admin forms that use nested_admin.