No way?! lol
Warming up the ECU points to a problem with conductivity of one or some of the components as the warmer something is the better it conducts and vice versa, could be a dry solder joint or a faulty component IMO, either way a different ECU should sort it out
As I mentioned before this is the trouble with 20 year old ECU's, looms and components, even if you buy a 'good' one it could fail any time
I'm sure Jano will be happy to send you another one in exchange though!

So around 155bhp now and around 200bhp in April, nice nippy motor!