It probably isn't the plug that's loose; it just seems that way because the core sits loose in the housing. If the plug itself was loose that'd be a sign of extreme wear and in most cases that'd actually make the lock much easier to pick because the tolerances would be so poor.
What you're describing sounds like a false set, I'm not familiar with american brand names but I'm pretty sure I've heard mention of defiant locks having spools in them. Simple enough to pick past if you know what to feel for, do some reading on those and you should pop it in no time.
