I would check the AI first using the "test defense AI" because it sounds like it is not calling your custom play.
Whatever results you get should add up to 100% or at the very least more than 100%. Per Bort it is suppose to just add up all the options. Then use those options numbers to calculate the %. So it you only had 1 output option at 10%. It should calculate it as 10 out of a total of 10 and get to 100%. But I don't trust that it works.
I know several seasons ago there was a bug that was calling random plays on offense when the % was not = to 100%. Bort supposedly fixed it. But every since then I try to make sure the % is 100. Since we ended up calling a random play. Had only 2 WR's out in a pattern on 3rd and long. I think they both ended up triple covered. The result was a pick 6 that cost us the game and making the playoffs......