Issue Key Hyperlinking is failing when using certain Regex in jira.projectkey.pattern

Summary

JIRA does not appear to be correctly creating issuekey hyperlinks (eg JRA-1234) with certain regex when it should be able to.

Steps to Reproduce

1. Create a new issue and comment on it with a link to another issue (so we can see hyperlink behaviour working). This can be done with the default project key pattern.
2. Change the jira.projectkey.pattern to be the following:

   [A-Z]+[0-9]*
   

3. Reload the issue.

Expected Results

The issue key hyperlinks correctly.

Actual Results

It doesn't as per the attached example.

Workaround

This can be worked around by using a different regular expression, for example, ([A-Z][A-Z]) is the default. And to provide similar functionality for [A-Z][0-9]* (allow numbers), the following can be used:

([A-Z][A-Z0-9]+)