After clicking "create" (submit) on the create issue dialog, a spinner comes up. Occasionally this spinner goes away and the issue is created but the dialog itself doesn't go away.

This introduces the opportunity for me to create duplicate issues.

Additionally, there is no way to recover besides opening a new tab, and clicking on the "issues" drop down in order to check that my issue was indeed created. The reason that there is no way to recover is because the create dialog obscures the underlying content thus making the navigational elements of JIRA unavailable.

For a novice computer user, for example one who doesn't understand tabs well, I would be faced with the decision to either:
a) Click create again and hope it works this time (thus creating a duplicate issue)
b) Hit cancel in the hopes that my issue had actually been created with the risk of losing the data that I had put into the create dialog.