Our robot UR 10e showed fault every 3rd cycle.  we have a RG6 gripper attached and rail venation software. 
1. It shows us a fault with ToolA: C740A0 Hardware monitoring:
2. Critical error and tool connector. the ground pin is outside of the allowed range.
Can any one with this issue to solve with the errors? 

Sounds like you have a short at the tool flange. What do you have connected to the tool IO port?

I do not connect anything, RG6 is the only tool i connect

Can you replicate the issue with a program that does not rely on the RG6 so that you can unplug it and see if there is an issue with the gripper? 

It is working after I  change the speed of the robot from 100% to 80%. So, RG6 gripper works at lowest speed? 

Possible, maybe there is a short in the cable and at slower speeds it does not shake as much and so does not short.  Same thing if there were a short inside the gripper itself, the issue may be made worse by going faster.

I will run with 80% or replaced by other RG6 gripper . Thank you Matt

How much will be the circuit board of the controller?

You’ll have to ask the distributor you purchased from as they will have to order that for you.

Hello, did you manage to figure out the cause of this error ? I am having the same and it mostly happens at the startup of my robot and when the gripper is going through the Reset and Activate sequence.