Django trying to save object with existing primary key
Solution 1:
After a long research I've found the solution. I'm using POSTGRES and Django uses PostgreSQL’s SERIAL data type to store auto-increment keys. A manual primary key assign stops the pk auto-increment. The solution: sqlsequencereset
$ django-admin sqlsequencereset app_label
"Use this command to generate SQL which will fix cases where a sequence is out of sync with its automatically incremented field data."