Interesting... I have not heard of that particular error before.
Help me understand - you said LB3500, do you mean the original LB3500 sold in 2009 or do you actually have an LB3510 or LB3510 Brushless?
Nevertheless, since the issue happens near the border most of the time, it could be a hint that the problem is a signal issue. Send your email address to info@paradiserobotics.com and I will email you our signal troubleshooting guide.
RobotLady