Chuck many thanks thought so,
Yes I have gone thru Calibrating CTT proceedure and aware of the specific requirements for the signal.
Have all the stuff needed to do it.
As I have mounted a subsitute A5 bd need to replace to the original and do a full CAL anyway.
However it means that the original OPT board has an issue that caused the other flaky tests as orig OPT bod ALL CTT tests fail.