Some issues from JIRA are not synchronized to SpiraTeam

Hi,

I'm integrating SpiraTeam with our existing Jira installation (v5.1.6). Plugin used (Jira 4.x / 5.x) works as expected, however it does not synchronize some Issues (half of them), we currently have ~630 issues in JIRA, even if I tried the "Force Re-Sync" button in Data Synchronization Admin section.

Types, Statuses, Priorities and Severities were all recreated to match our JIRA installation and were properly configured in data mapping.

Could you please give me a hint on what can be the problem?

Thank you.