I design fairly large forms, that span multiple breaks, and so I use the duplicate field feature a lot.
I've recently encountered an error which I thought may have been related to server memory, but as it turns out - disabling plugins, increasing memory etc, all didn't seem to help.
The symptoms are a form which displays perfectly in admin, but displays a blank preview form (still has the header, and message that the page might display differently - but there are no fields or buttons displayed).
Luckily I update regularly and constantly check using preview so I was able to pinpoint the field which was the problem and it was a problem caused by duplication.
Why it buggered the form I don't know, but I managed to duplicate a copy of the form with the error causing input field in case you guys wanted to check it out. Just hit me up and I'll give you access to trouble shoot what caused the bug.
Simply deleting the field fixed the form - but I can imagine this would cause nightmares for people who create lots of forms and end up troubleshooting in the wrong place.
