The EWD has changed. It now starts degrading as soon as you you have an average tech level of 1. Yes, one.

The way the old ewd worked is it became useless as soon as you hit an average tech level of 18. It would never trigger on it's own from that point. Basically take the level the EWD starts degrading and add 10 to it to get the level it stops working completely when you are attacked.

The EWD now scales up depending upon your average tech level. At an average tech level of 1 you have a 95% chance it will work, level 20 is a 50% chance and level 40 is a 5% chance it will work.

So the higher your ships average tech level the more likely the EWD will fail.