Do you do any pre-stretching and warm up exercises before practice.. Sometimes it's just a matter of shaking you hands out to loosen up every once in a while.. Are you using a metronome or drum machine to keep time..? Counting time is important. That's a few more thing to think about..
On the wide neck classical, I didn't have as much trouble as I thought I would. It may depend on the experience or lack of..
Again, don't let a little hiccup frustrate you.. life is full of up and down cycles and guitar playing is no different..