Thanks for all of the input guys,
I have bought an rcexl unit and will install and test tomorrow. The problem was occuring on an Evolution engine with the ignition unit that evolution supply, not the rcexl type.

MTK, I forgot to mention that I swapped out the batteries as well, just in case. No difference.

I will post back if the problem has been solved with the new unit. Fingers and toes crossed.

Cheers,

Peter