According to the service manual which you can download from the Universal Robots support site a C75 error is an encoder error, but the C75A65 code is not listed in the charts. However, the solution for the other C75 errors is replacement of the joint. @Stefan_Stubgaard can you provide any additional information?

@matthewd92  can we solve the problem by  Adjust encoder.

Not that I am aware of. I will see if I can find out more information today as I am near some of the UR folks today. 

@sjhassan14 I spoke with UR today, the only solution is to replace the joint as the encoder has failed. 

@sjhassan14  If your robot is still under warranty it will certainly be voided if you attempt an modifications in the joint.  If it is out of warranty then you can proceed at your own risk.  UR does not publish any material on doing this, so it would all be on you to determine how to do it properly.  I do not advise this.

thank you @Grady_Turner , our Robot is Under warranty, so i will contact the Universal Robot representative.

I have similar problem. The new robot UR3 was delivered. It was ONLY switched on third time after delivery and this fault message appeared > BASE : C75A1 : Joint encoder error : Invalid decode : Readhead misalignment, ring damaged or external magnetic field present. According to service manual joint should be replaced. Is it luck or I should expect more pieces like this ?

@Jose I can say that we’ve only seen 1 encoder issue in the field and we have a lot of robots that run a lot of hours every week. From my experience you should not expect to receive robots that have issues, this is a fluke. 

Has anybody else experienced this issue ? Wrist 2 C75A1: Joint encoder error.
I had to replace a UR5 in my factory today. I was unable to move the arm in manual mode at all.