Step to reproduce the issue:

1. Integrate Confluence with a JIRA instance and create the application link.
2. Create a new page and type quickly the following string:

   {JIRA: FP-2}
   

   which FP-2 is one example issue key on JIRA.

3. Save the page

Expected behavior

The JIRA issue link from the JIRA issue macro should be "<JIRA base URL>/browse/FP-2"

Actual behavior

The JIRA issue link from the JIRA issue macro is "<JIRA base URL>/browse/+FP-2" which point to a dead link.

Workaround solution

Open the JIRA issue macro UI then save it should help in this case.