Bear in mind that, if there's a problem, a lot of people will be looking for a solution, so what you're seeing is likely to be the whole iceberg, not just the tip. You'll also find that a lot of the listings on Google are referencing each other, so three or four entries may well be the same thing.
There isn't a problem with Lollipop itself, but the update process can go wrong for a variety of reasons. I rather suspect that the system state at the time it's done may come into it and, for that reason, I'd always at least to a simple restart before performing one. That way, only the basic processes should be running. On an older device with limited memory I would (and always have) done a factory reset first, which makes sure there isn't a raft of apps loading their own processes that can get in the way.
In most cases, a factory reset after the event will smooth things over as it gets rid of any bits of the old system that are hanging round in the cache and confusing things. If this doesn't help, you'll need to send the device off for repair as it's likely that a clean re-flash will fix it. A Sumsung service centre if probably the best place for this.
