RobotStudio event

PCSDK ReadUIInstruction() fails

Several machines in production, all using PCSDK will eventually fault with this error:

An exception has occurred.
Message: Attempt to access the method failed.
Source: ABB.Robotics.Adapters.IRC5
StackTrace:    at Adapters.Rapid.ReadUIInstruction(String taskName, String stackUrl)
   at ABB.Robotics.Controllers.Internal.UIInstruction.ReadUIInstruction(String taskName, String stackUrl)
InnerException: 

An I-start will resolve the issues, but it will occur again in time.  How can I go about resolving this issue?  Any help/advice would be appreciated.

Thanks,
Dan.