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Changes between Initial Version and Version 1 of Ticket #33984

initial	v1
1		I'm upgrading our codebase from Django 3.2 to 4.1, and came upon a regression when running our test suite. I bisected it down to commit ~~[4f8c7fd9d9 Fixed #32980 -- Made models cache related managers](https://github.com/django/django/commit/4f8c7fd9d91b35e2c2922de4bb50c8c8066cbbc6).~~
	1	I'm upgrading our codebase from Django 3.2 to 4.1, and came upon a regression when running our test suite. I bisected it down to commit 4f8c7fd9d9 Fixed #32980 -- Made models cache related managers: [https://github.com/django/django/commit/4f8c7fd9d91b35e2c2922de4bb50c8c8066cbbc6]
2	2
3	3	The main problem is that when you have fetched a model containing a m2m field from the database, and access its m2m field the manager gets cached. If you then set the model's `.pk` to `None` and do a `.save()` to save it as a copy of the old one, the related manager cache is not cleared. Here's some code with inline comments to demonstrate: