Hope you are doing well.
I encountered this issue while troubleshooting a security role, Like users belonging to a custom role were not able to post the invoice journal.
Access denied to method TRANSFER of class LedgerPostingGeneralJournalController
1. Go to the specific role and Click on "Override Permissions" as shown below
2. Click on Add Server methods
3. Filter the LedgerPostingGeneralJournalController/transfer method and add it to the list of permissions