Help! My ignition is dead!

So, if both units are faulty, but not a simultaneous failure, the engine will start on the good one only, then run on both normally. When the second unit fails, it won't start. Correct? And is this all true even if the units pre-date the introduction of "soft start"?

And, how does the ice pack idea work? I am in Thailand, where it is rarely below 29 Centigrade, I don't know where you are, is it also a hot climate?

Yes you are correct in your explanation of the problem. I am in the uk and the problem exists here too. It is due to component failure or drift which is more of an ageing process. 

I am not exactly sure of the root cause but I suspect that it is to do with one of the semiconductors which is why the ice pack changes the performance of the components sufficiently to start the engine. 

As you correctly identified in your initial post, everything else is duplicated so it is unlikely there is a common cause elsewhere. 

Mine were pre soft start modules. 

In case you need to exchange the modules do your engine and yourself a favor and go for the simply better Ignitech modules. I replaced fully functioning Rotax modules for them and I am impressed, would not change them back. Engine runs smoothly at all rev settings, idling at 1300-1400 revs with no rumbling at all. Plus, their purchasing-resistance is low. I‘m not 100% sure but the repair effort is about the same as their new price.

So I managed to borrow two modules, of indeterminate age an condition. Fitted them, all works perfectly!

Thank you for the responses, Kevin particularly.