The issue cockpit block is completely cached including strings and therefore, it's not ok for i18n enabled websites.

There are two possible solutions:

Either use the language iso code in the cache id (line 1734 in project_issue.module):

if (module_exists('locale')) {
  global $language;
  $cid = $language->language;
}
$cid = 'project_issue_cockpit_block:' . $cid . $node->nid;

But a better solution would be to cache the variables only which are used in the template, as a serialized array.