2006 Fiat Punto

I have a Fiat Punto Active Sport 1.4 2006. I went out to start it one frosty morning and there was nothing. I turned the key all the dash lights came on, interior etc but the display showed “Power Steering Fault, contact dealer”. I called out rescue but they had to tow it to the Fiat garage where I bought it. They put the battery on charge and it seemed to run a bit lumpy for a day then 2 days later same problem. The car went back to the garage and on diagnosis they recommended a new main engine ECU which was fitted. All ok until this weekend. It had rained loads and I was camping so the car was sitting on damp grass overnight. Saturday morning, same message, nothing when I turned the key. Is this a common fault? We waited about 45 mins and it started and has run fine since. I don’t want this to keep happening and is there a preventative measure e.g. can I try to seal with waterproof tape the ECU or somewhere where damp must be affecting the component?