Jira Bulk Issue Creation changes on sub-task creation?

Recently we created some code which automated project and issue creation for a client.
After our last sprint at the end of september we were creating bulk sub-task by specifying the name of the issue type to create.

Now the same code fails as it demans the id of the issue type to be specified.

Has there been any changes on bulk issue creation?
Is there any place where we can find a change log on the API if something like this were to happen in the future?

Thank you in advance.