Incidentally, if the root cause of the twitch could be isolated and demostrated on demand, that would be useful too, though its more of a 'would be nice if' rather than a mission-killer.
The way to handle that situation is to comment-out code until the problem disappears. The last thing removed is the most likely culprit. I suggest starting with SoftwareSerial / lcd. Comment-out the declaration and let the compiler lead you through the rest...
// SoftwareSerial lcd(2,6);