[Answered ]-Pk reference in Django related models

The Unique error is most likely because the update_or_create is just trying to create and then getting conflicting primary keys.

Because you are already getting Model1 here: model1 = get_object_or_404(Model1, pk=pk) you could just replace the update_or_create with:

model1.status = 'closed'
model1.save()

Note: I didn’t originally post this as an answer because I wasn’t sure if update_or_create was mandatory or not.