3DS errors

How common is it to experience errors when playing a 3DS? I've had mine for a couple months now and until a little while ago, I never had a game freeze once, but it did so for the first playing during a boss battle in Bravely Default.
For those who play this system, is it normal for it to do this a little when you haven't had it for long? And when it does, what are some causes?
I've been taking good care of the system. I store it in a 3DS carrying case and it's never fallen on any objects before.
I have however played it lying in bed on a number of occasions, holding it in a slightly slanted position, but I haven't done that of late.
Hopefully, I won't have to replace the system. I've really enjoying Bravely Default and I don't want to have to stop playing anytime soon. I especially hope that if it does freeze again, it won't do so during a boss battle.

My 3DS has never misbehaved itself.

This is the first time I even hear about a 3DS freezing.
I wouldn't count on it happening again.

That's good to hear. I would not want it to happen again during a boss battle, especially one that's hard to beat regardless of levels.