No Start issue - UPDATE kinda long

Ya know, I've seen a similar issue twice in the past year. Start checking stuff after it won't start. Solved it twice now by swapping out ECUs, not sure why tho. I know they're both good. Was starting to think it was the ECU plug connector getting flaky. Must be tickling that ground when I do the swap. Gonna add a ground wire to the block somewhere and see how it goes.