1970 Dodge Dart Door Latch Question

I have a 1970 Dart and the door won't open when using the inside door handle. It opens from the outside handle just fine. Everything is lubed up and seems to be functioning, but it just won't open using the inside door handle.

Before you tell me that it's sagging hinges, know that it won't open when I manually latch the door when it's open. So that's not it.

Anyone have any ideas on what the problem is?

Can I just buy this one from Classic Industries or is a 1968 Dart have a unique one year door latch?
1968 Dodge Dart Parts | 2862771 | 1968 A-Body Front Door Latch; LH | Classic Industries

Thanks in advance for the help!