Sorry about that - once it's queued it's normally safe and will be processed so yes, re-submitting it will just result in duplicates and may actually cause posting limits to be hit which then delays things further (same for posts). The system "rewards the patient", LOL
Sometimes though things do get stuck, the queue stalls or some other housekeeping task get's launched by a careless admin who forgets to run in on the lower priority queue (the same admin who really should swap the default queue so that doesn't happen).
The servers can get a bit slow if there are attacks happening on the site. I will look at the scaling settings to see if the impact can be reduced and am working on a new version that will be significantly faster which I hope will help. There's also some options for having instances run in the European data centers which will make things quicker by being closer.
I'll also look at the posting limits for established & trusted posters.